If one does not understand the words of a blessing or thinks of other matters while reciting it, according to some opinions it is considered as if he did not recite the blessing at all and is hence required to repeat the blessing. This applies even if he said the blessing in Hebrew. Practically one is not to repeat the blessing although initially one must be very careful to concentrate while reciting blessings.

Not to do any Melacha while saying the blessing:[2]

One is not to perform any action that requires concentration while reciting Asher Yatzar. One is not even to learn Torah while reciting it as all blessings initially require concentration according to all. This applies by all blessings.

May the blessing be said while one is drying his hands?[3]

If doing so will not disturb one’s concentration of reciting Asher Yatzar then it may be done. However some Poskim are stringent in this matter even in such a case. Likewise some avoid reciting the blessing until the hands are dry.

Reciting each word with attentiveness:[4]

One is to say every word of the blessing of Asher Yatzar with concentration, holding in mind the great kindness that Hashem does with man, as explained above.

Segula for cure and preventive healing:

The saying of Asher Yatzar with proper concentration is a great Segula for cure of ailments. In the words of the Seder Hayom: “If a person is complete in his attributes and he carefully utters his words he will not become sick all of his days and will never need a doctor. Certainly then one is to say the blessing with strong concentration and a complete mind to the healer of all flesh.”