Things I consider: 3-bet %, fold to 4-bet %, history notes, c-bet %, stack size.
Obviously, the more junk they have in their range, the more we can widen our range & play back at them. There's a good chart in the HEM article (facing a preflop 3-bet) that tells
you how often they have to 3-bet in order to stack off with JJ/AK/AQ/TT preflop.
fold to 4-bet %:
Once again, this is pretty obvious. There are some ABC nits that can fold AK preflop, blind vs. button. I abuse them. There are some lag-tards who stack 44 preflop. I 4-bet/call with 77.
Usually if I'm playing the 3-bet/4-bet game, its with regs, and history plays a big part here. Anytime a 4-bet hand gets to showdown, or I've 4-bet and folded, I made a note. Regs remember that. So if I've recently 4-bet smallish and folded, I'll 4-bet small with aces.
I mostly look at this number when deciding to flat a big hand. If they 3-bet a huge percentage, and c-bet every flop, I start flatting QQ+/AKs. Its just a much better way to get additional money from their weak range (since 4-betting folds most of it, usually).
200bb's deep, I start flatting a lot of stuff. Suited connectors, small pairs, suited aces. When you open to 3xbb's, and they 3-bet a pot sized raise ~10bb's, the stack to pot ratio will be about 10:1, and you're usually getting odds
So yeah, just use yer brain. Lots of guys 3-bet light tons of junk from the blinds, and insta-fold to 4-bets (no one stacks off with T4o). So obviously calling in position and letting them c-bet is the best way to take their $. Some spazzes 3-bet/call shove with 44, so stack them with pocket 9's. Some guys 3-bet AQ 200bb's deep, and just call it a cooler when they flop TPTK & you flop a set. Some are ABC tags, and they 3-bet, c-bet, and give up. Use your stats, reads, and figure out the best way to get them to make a mistake.