You have to pick your spots for sure and I think for each player these spots depend on what we are comfortable with doing.
I like to 3bet alot of my weaker hands and alot of my strongest hands - hands like AK, AQ, JJ+ are all generally 3bets for me because they are some of my strongest holdings - I also elect to 3bet KQo, KJ, 89s, 9Ts, A6-A8 (because these are the worst aces in the deck) and hands of that nature because they are some of the weaker hands I can have and I dont mind giving up weak hands to an incoming 4bet - otherwise the 3bet allows me to take control of the pot and I can proceed post flop accordingly. A8 will play much better as a 3bet than just a flat behind, if we 3bet, flop an ace - cbet - and get the fold, it was a much better scenario than flatting preflop and having to check-call down possibly 3 streets. I hope some of this is making sense...
What I am saying for 3betting is we want to mix in some of our weaker hands with some of our strongest hands - flatting alot of medium strength hands in between. If we are only 3betting our strongest hands we are allowing players to exploit us by folding and denying us further action. I also only tend to 3bet when I have a comfortable stack 35+bb's - 3 betting to 8 or 9bb on a 20bb stack gets awkward pretty quickly when called.
Squeezing is relatively similar if you have a limp or two in front squeezing is essentially the same as 3betting in a sense where we want to do it with our strongest hands and some of our weaker hands - when we get called, we can play accordingly post flop. Some players will look to limp-reraise their strongest hands but I find more often than not that limpers in general are more often weaker than they are strong. I also like jamming as a squeeze when I am on a 20-28bb stack. If our button opens 3x or less and say we have A8s in one of the blinds - I will 3bet jam as a squeeze from the SB/BB - this is highly effective against most button raises and will get through quite a bit - and, when called, we are often not in terrible shape. In fact we can get called by some weaker suited Ax and strong Kx hands quite often when players have bigger stacks and in those situations we are in good shape and should be first pumping that we got called by worse.
Both situations are all about timing and solid post flop fundamentals - make sure whenever you do decide to 3bet or squeeze that you have a plan for when you get called or raised. We dont want to be doing these things blindly and without reason - we have to have a strategy in place for whatever happens next!
Again I hope this helps, hope it makes sense. Take care, good luck in your games.