Shulchan Aruch 489:1 says that after Maariv of the second night of Pesach we begin to count Sefiras HaOmer. The Mishneh Brurah there in note 2 says that one should count before "Aleinu" because "col ...
What are the general rules regarding doing activities (such as eating or checking email) before mitzvot (such as tefillin or prayer)?
Imagine that there's an mitzvah which I can do. It might be obligatory, or it might not be. For example, tefillin, prayer, kiddush, havdalah, shofar, feeding my pet, visiting the sick, Torah study, or ...