Hi and welcome to FTR. Good to have you here!

There's no need to focus on every single player for every single hand. Just focus on the active players in each hand. For example, if three players fold and the fourth raises, have they been raising every hand or is it their first raise? Have they folded every hand previous to this one or have they limped in? What hands (if any) have they shown down previously, have they been weak or strong? Also, don't worry about trying to put players on exact hands, nobody (well, maybe with the exception of Daniel N or Phil I) can do this, focus on the range of hands that opps might hold.

Probably the best way to learn is to just go ahead and post the hands about which you were unsure with as much background to the hand and situation as you can remember and we can go from there. BTW if you're playing sit-n-go tournaments, feel free to post in the Sit-N-Go Tourney Tactics forum directly (that's where I usually live).

Again, welcome!