Laws relating to the cup of wine:
The cup of wine used for Havdala follows all the laws which apply by a Kos Shel Bracha, such as by Kiddush and the cup used for Birchas Hamazon. The following is a summary of the applicable laws:
- The cup is to be washed inside and outside.
- The cup may not be damaged.
- The wine is not to be Pagum.
- The cup is to be lifted three Tefach from the table
- The cup is to be received with both hands.
- The cup is to be held only in the right hand.
- One’s eyes are to be on the cup.
Overflowing the wine: It is customary to pour enough wine so that it slightly overflows from the top of the cup. [One is to have an undamaged plate under the cup of wine, having the wine spill onto the plate. One is to throw out the spilled wine after Havdala.]
If one said Havdala and then realized there was a hole in the cup, does he need to repeat Havdala?
Some Poskim rule that if wine was dripping out of the hole then he is required to repeat Havdala. Others however rule that one has fulfilled his obligation, and there is thus no need to repeat Havdala. It appears from Admur like this latter opinion.
[According to all if one had wine on the table at the time of the blessing, aside from the wine in the cup, then he may drink that wine without needing to repeat Havdala or the blessing of Hagafen.]
If one said Havdala over wine and then when he tasted it noticed the wine is spoiled or is really colored water, must he repeat Havdala?
One had a bottle of good wine on the table: If one had a bottle of actual wine on the table at the time of the blessing, then if he had in mind to drink more wine after Havdala he is to drink that wine without needing to repeat Havdala or the blessing of Hagafen. If he did not have in mind to drink more wine after Havdala then although he has fulfilled the blessing of Havdala he is to drink that wine and repeat the blessing of Hagafen.
One did not have any good wine on the table: Most Poskim rule he must repeat Havdala over wine, omitting however the blessings of fire and Besamim. However some Poskim rule he is not to repeat Havdala. According to them he should however try to hear Havdala from someone else.
If one said Havdala over wine and it spilled prior to having a chance to drink from it what is the law?
If there is even a small amount of wine remaining that he is able to drink then he should drink from it. After drinking this wine he should pour himself another Revius of wine and drink it without saying a blessing.
If there is absolutely no leftover wine that he is able to drink then the following is the law:
One has a bottle of wine on the table:  If one had a bottle of wine on the table at the time of the blessing, then if he planned to drink more wine after Havdala, he is to drink that wine without needing to repeat Havdala or the blessing of Hagafen. If he did not have in mind to drink more wine after Havdala then although he does not need to repeat the blessing of Havdala he is to repeat the blessing of Hagafen and drink that wine.
May wine which was left open, or left in a cup be used for Havdala?
If it has been left in the open for many hours [3-4 hours] it may not be used for Havdala.
 271/18; 296/2
 See Shulchan Aruch Chapter 183. The full details of these Halachos will IY”H be printed in the Volume that contains “The laws of Kiddush”.
 According to Halacha [183/2] there is no need to wash the cup if it is already clean. Furthermore even if there is leftover wine it does not need to be washed unless it has pieces of bread inside. However based on Kabala one is to always wash the cup before using it for Kos Shel Bracha even when clean. [Kaf Hachaim 183/4]
 Being Mitaken the wine with water: Based on Kabala one is never to add water to the wine when the wine is already in the cup. Therefore one is to add the water to the wine while it is still in the bottle. [Ketzos Hashulchan 97 footnote 1 from Shaar Hakavanos and Mishnas Chassidim]
 Likutei Taamim Uminhagim, brought in Sefer Haminhagim p. 55 regarding Kiddush; See Shaareiy Halacha Uminhag 1/103 that it is lifted three Tefach as a Hiddur, and so is sourced in different places in Zohar.
Opinion of Admur in Shulchan Aruch: Admur rules [183/8] that one is to lift the cup one Tefach from the table in order so it is visible to all.
 296/5: “It is customary to pour a little wine from the cup onto the floor. It is to be done in a way that one slightly overflows the wine while pouring, and lets it spill to the ground. It is best not to accomplish the above by filling the cup to its top and then spilling some wine from the cup. The reason for this is because if one follows the latter custom he will end up not having a cup filled to its very top as is the commendable practice. Furthermore, he cannot as a result of the above reason say Havdala on a full cup without spilling wine out and then prior to drinking the cup after Havdala spill out some wine. The reason for this is because doing so is a belittlement to the blessing of Hagafen which was said over a full cup, as now when he spills some out it appears like there was something repulsive in the wine which he said the blessing over. Therefore the spillage of wine is to only be done in the above mentioned method.” [ibid]
The reason for overflowing the wine: This is done for a good omen, as any house which does not have wine spill like water does not contain a good omen. Therefore we practice an act of good omen in the opening of the week. Doing so is not forbidden due to it being considered a belittling of food, despite that the wine goes to waste, as one is only spilling a small amount of wine. [ibid] This is based on the Magen Avraham [296/3] which explains that on a small amount there is no problem of Bizayon. However the Taz [296/1] explains that in truth there is no good omen involved in wasting wine. Rather the good omen is if wine happens to spill and one does not get angry. Nevertheless he agrees with custom to overflow a small amount of wine.
Other Reasons: Some write one is to pour the wine in order to weaken the Kelipos, as wine is the Gematria of 70 which corresponds to the seventy nations. By spilling the wine one weakens their strength. [Mateh Moshe 504]
Other Opinions: The Rama 296/1 rules one is to pour the wine prior to the blessing of Hagafen.
 Shaareiy Halacha Uminhag 5/31
 Shaareiy Halacha Uminhag 5/31; This custom is also brought in Minchas Shabbos; Ketzos Hashulchan 97 footnote 2
As for the reason why we do not spill the wine on the ground, as mentions Admur [brought in previous footnotes], perhaps this is because we suspect for those opinions which forbid spilling onto the ground, as well as the opinion of the Mekubalim which negate this custom. Hence we over pour the wine onto a plate which hence is not a belittlement towards it. [See M”A 296/2-3; Taz 296/1; Kaf Hachaim 296/10-11]
 It is necessary to spill out the wine as the entire purpose of the spill is so the wine go to waste and be treated like water. [See Shaareiy Halacha Uminhag ibid]
 Mishneh Berurah in Shaareiy Tziyon 183/14, as in such a case the cup is not considered to hold a Revius and the holding a Revius is required even Bedieved.
 Sheivet Haleivi 9/41; As the law of requiring a vessel is only Lechatchilah, as the Sages only required a vessel by Netilas Yadayim even Bedieved. However by Kiddush and Havdala no such institution was ever made. Thus Bedieved it remains valid.
 183/4 as Admur says that the breaking of vessel is its death, and nevertheless concludes that one is only to be stringent when possible. Thus implying that Bedieved it is valid.
 271/28 as holding the cup of wine in one’s hand while saying the blessings is only required initially, while after the fact it is valid even if the cup remained on the table. [ibid]
 271/28 regarding Kiddush. The reason it is valid is because holding the cup of wine in one’s hand while saying the blessings is only required initially, while after the fact it is valid even if the cup remained on the table. [ibid]
 So rules Piskeiy Teshuvos 296/10 based on Ashel Avraham Butchacher 296
 Whenever one did not have in mind to drink more of the wine in front of him then a new blessing must be made if he did not drink the wine in his original cup. [So rules Admur in 206/11; Seder 9/8; Rama 209/2]
Other Opinions: Some Poskim rule that by Havdala one may be more lenient even if he did not have in mind to drink any more wine, as one certainly had in mind to fulfill Havdala as required by the Sages. [Ashel Avraham Butchach 296] The M”B [206/26] rules that whenever one has more wine in front of him even if he did not have in mind to drink any more wine, he does not repeat the blessing of Hagafen.
 Based on Admur 271/28 regarding Kiddush and so rule explicitly regarding Havdala: Chida in Chaim Sheal 74/43; Pischeiy Teshuvah 296; Birchas Habayis 46/21; Minchas Shabbos Shiyureiy Mincha 96/3; Piskeiy Teshuvos 296/10
 Kaf Hachaim 296/21
 As the Tur brings the Pirkeiy Rebbe Eliezer which rules if one does not have wine he may say Havdala without any beverage. Now although we do not rule like this opinion, we should suspect for it to not require a blessing in vain, as is the rule by Safek Brachos Lehakel. [ibid]
 See Ketzos Hashulchan 79 footnote 23
One is Yotzei Havdala in such a case as rules Admur in 271/27 regarding Kiddush. One is also does not have to repeat the blessing of Hagafen on the new cup of wine in such a case as rules Admur in Seder 9/5; 206/9
 271/28 regarding finding water or spoiled wine in the cup and the same would apply here that the wine spilled. The reason it is valid is because holding the cup of wine in one’s hand while saying the blessings is only required initially, while after the fact it is valid even if the cup remained on the table. [ibid] See also Ketzos Hashulchan 79/6 which rules this way regarding Kiddush.
 Admur rules that even when one has wine in front of him he only saves himself the need to repeat the blessing if he had in mind to drink the wine that was on the table after Kiddush [so is implied from Admur 271/28 from the words “prepared to be drunk” and from the KU”A 8 and so rules Admur explicitly in 206/11; Seder 9/8; Ketzos Hashulchan ibid]
Other Opinions: The M”B [206/26] rules that whenever one has more wine in front of him even if he did not have in mind to drink any more wine, he does not repeat the blessing of Hagafen.
 271/27 and Ketzos Hashulchan 79/6 regarding Kiddush and the same applies for Havdala; So rules Piskeiy Teshuvos 296/11
 See however Ketzos Hashulchan 79 footnote 24 that if one has wine in the house and had in mind to drink more after Kiddush [or Havdala] then it is as if it is sitting on the table and one is not required to repeat the blessing of Hagafen.
 Biur Halacha 272 Biur Halacha “Al Yayin”; Ketzos Hashulchan 46 footnote 2.
Other Opinions: Rav Akivah Eiger leaves this matter in question. See Biur Halacha there.