The moon should be half full or more. This narrows the choices to about 180 days in a year.

It would be best is when the moon is either full or half. This all narrows it do 3 days per month, which is 36 days in a year.

Finally, try to find a full or half moon that is also in a “sweet” or “steady” nakshatra (Revati, Citra, Mrgashira, Anuradha are sweet. Rohini, and the three Uttaras are steady). This will narrow it down to much less than 36 options!

If you cannot find a day like this that is practical for you, go with any day where the moon is half-full or more, and in one of the above nakshatras. (If you know how, try to avoid the 11th and 13th waxing, and the 4th waning phase.)