Good question that a lot of players find themselves asking. It's a lucrative spot when you pick up a premium hand in the BB and there is action before you. I think in general players don't 3bet squeeze or 3bet from the BB enough. As there are endless scenarios and variables to every hand and table, I think it's hard to give a definite answer, but in general I think squeezing from the BB vs 2+ opponents should be a pretty tight range(AK, AQs, JJ+). You can mix in the occasional
bluff with suited wheel Aces, KQs, suited connectors-but I generally would rather play a hand like that post flop. When action folds to CO, BTN, or SB though, we can 3bet with a much wider range, especially if said opponent is chip leader at the table. I think vs CO and BTN we can 3bet profitably with any suited Ace, pocket pairs 77+, some suited Kings, and also obviously the top of our range that we aren't slowplaying. 3bet bluffs can literally be almost our entire range. As long as we aren't 3betting every hand and have a somewhat tight image, we can get hands like K9, KT, KJo, weak aces and small pairs to fold pretty easily and pick up some easy chips.
Vs SB is pretty much the same but with an even wider range. If action folds to SB, we can 3bet bluff with 100% of our range. I actually prefer 3betting with weaker hands in this spot since we already have dead money invested and we can get a TON of hands to fold(if opponent isn't a calling station). Since we can 3bet bluff with our entire range vs SB, our actual 3bets for value shouldn't really matter, as long as we aren't always 3betting blind v blind. I will even mix in some flats and checks with stronger hands(pairs, suited broadways) to keep them guessing. It really all depends on the tendencies of the player in the SB, same goes for BTN and CO. If they are sticky/a station, all of that goes out the window and I'll stick to a more ABC poker 3bet range(premium hands).
Vs EP, I'm hardly ever 3bet
bluffing from the BB. Any suited connecting hand plays well post-flop, so there's no reason to inflate the pot vs EP who has a much stronger range than us. I'm sticking to my 3bet squeezing ranges here, possibly even a little tighter, and only really bluffing with hands that block premium hands(KQ, KJ, Ax).