Yes yes and yes..

I take pretty detailed notes during the tourneys.. (i only play one table at a time now.)
I look for any hand that goes to the river and I write down notes, what they'll raise Preflop with, How they play top pair with what kind of kickers..
Will they play "Any 2 suited" What the'll call PFR's with.

I used to play 2-3 tables at a time but I felt I wasn't able to keep track of them. Now I play 1-2 at a time but take MANY more notes.

As for looking for weak players before I sit down.. Yes i do. I added a few intersting players to my buddy list and check it before I sit down.

One other thing I do is go back through my hand history a day or two after I play the hands/tourny. I critique my play and what I did/didn't do so I cna help spot weakness in my play (yes there is quite alot in there) Even as I'm replaying hte hands I'm taking more notes on the players that I might have missed during the hand.