1. Together with keeping the musjid clean, also keep the musjid fragranced by burning oudh, etc.
عن عائشة رضي الله عنها قالت أمر رسول الله صلى الله عليه وسلم ببناء المساجد في الدور وأن تنظف وتطيب وقال سفيان قوله ببناء المساجد في الدور يعني القبائل (سنن الترمذي، الرقم: 594)
Hazrat Aaishah (radhiyallahu anha) reports that Hazrat Rasulullah (sallallahu alaihi wasallam) commanded that masaajid be built in the different localities, and that the masaajid be kept clean and be fragranced.”
عن ابن عمر رضي الله عنهما أن عمر بن الخطاب رضي الله عنه كان يجمر المسجد في كل جمعة (المصنف لابن أبي شيبة، الرقم: 7523)
Hazrat Abdullah bin Umar (radhiyallahu anhuma) reports that Hazrat Umar (radhiyallahu anhu) would burn incense in the musjid on the Day of Jumuah.
2. If you are feeling sleepy in the musjid then change your place by moving and sitting in a different place in the musjid, provided it is not at the time when the khutbah is in progress. Through moving to another place, one’s sleepiness will be removed.
عن ابن عمر رضي الله عنهما قال سمعت رسول الله صلى الله عليه وسلم يقول إذا نعس أحدكم وهو في المسجد فليتحول من مجلسه ذلك إلى غيره (سنن أبي داود، الرقم: 1119)
Hazrat Ibnu Umar (radhiyallahu anhuma) mentions, “I heard Rasulullah (sallallahu alaihi wasallam) saying, ‘When any one of you feels sleepy while he is in the musjid then he should move from the place where he is sitting to another place.’”
3. After the azaan has been called out, if you have not performed the salaah, then do not leave the musjid without a valid excuse.
عن أبي الشعثاء قال كنا قعودا في المسجد مع أبي هريرة رضي الله عنه فأذن المؤذن فقام رجل من المسجد يمشي فأتبعه أبو هريرة رضي الله عنه بصره حتى خرج من المسجد فقال أبو هريرة رضي الله عنه أما هذا فقد عصى أبا القاسم صلى الله عليه وسلم (صحيح مسلم، الرقم: 655)
Abu Sha’thaa (rahimahullah) mentions, “On one occasion, we were seated with Abu Hurairah (radhiyallahu anhu) in the musjid when the muazzin called out the azaan. After the azaan was called out, a man stood and began to walk (out of the musjid without an excuse, before performing the salaah). Abu Hurairah (radhiyallahu anhu) watched this person as he left the musjid and then remarked, ‘As for this person, he has disobeyed Abul Qaasim (sallallahu alaihi wasallam)’ (as Hazrat Rasulullah (sallallahu alaihi wasallam) has instructed that after the azaan is called out, no person should leave the musjid without performing the fardh salaah, unless he has a valid excuse).”