Quick reply for now. Actually it really varies quite a lot. Certainly I read the readings a number of times and I pray and I ask the Lord if there is anything particular he wants me to speak on and ask him to guide me. On Sunday I almost always write the homily and mainly stick to that. On weekdays more often than not I do not write down my homilies (though I am starting to post some written homilies on my blog). I may do some background reading from books or the internet. That is a quick answer. Maybe another time I can give a longer one. GOD BLESS