What is your strategy for assessing other players at your table?

I play only on-line, so obviously there are only things I can notice on-line.
1. Stats. Since I play at GG, I have only 4 stats in internal GG hud: VPIP, PFR, ATS, 3BET. High VPIP and significantly lower PFR indicates a weak player. If all the stats are very high it indicates LAG/Maniac. Opposite - NIT. If they bet to me on late position I check their ATS. If they 3bet to me I check their 3bet stat.
2. Limping - when they open-limp from EP, it usually means a weak player. I also note whenever I encounter limp-raise (I usually suspect AA/KK in such case)
3. Straddle - usually weak players not realising or ignoring the math behind straddling. I also note whenever I see some obviosly visible trends of straddling players - how do they behave when raised - do they call/fold/raise alot?
4. I note unusually passive behaviors like flatting with very strong hand preflop or not rising with very strong hand on the river
5. I note whenever I notice a very agressive action like agressive bluffing, betting higher than usual, betting strong with medicore cards etc
6. I note when I notice some unlogical behaviours like clearly overvaluing their hands, ignoring action of other players etc

A very interesting topic. You always have to pay attention to every player and how they place their bets. We all have different methods for evaluating one or more players. At the tables, I usually play passively so I can observe each player and keep track of how my opponents play. It's very important to keep an eye on your opponents.

When I'm assessing a table, I try to categorize everyone within the first few orbits based on how many pots they’re getting involved in and how aggressive they are at showdown

I like to start talking to everyone when playing live,want to know everything I can about them ,then I needle people just a little just to see who gets rattled easily,see if their nervous or relaxed,how they handle their chips,I watch all their breathing patterns all these things can make a huge difference when making tough calls or folds,I keep track of their betting patterns,opening patterns,what kind of size of bets they make to win pots and what kind they make when bluffing,if I find myself at a table where I cant get a handle on the players or most of them,I get up and look for a new table because at that point I figure Im the lamb their going to feast on

I assess a player based on the information I gather about him at the table. The rest is pure instinct.

Unlike many others, I don't take notes on players I regularly sit at the table with.

When I first sit down at a table, the first thing I do is look for 'leaks' in my opponents' game. For me, the biggest giveaway is seeing someone constantly limping into pots or calling 3-bets with marginal hands like K-7 offsuit. I also pay close attention to bet sizing—weak players often telegraph their hand strength by betting tiny when they’re unsure and shoving wildly when they finally hit