There are a lot of different things to think about during a poker hand. It would take more time than I'm willing to give to outline them all here.
Generally speaking, my thought process starts with putting my opponent(s) on a range of hands and then trying to narrow that range with every new piece of information I receive.
Here's a generic example (my basic thought process will be in parentheses),
A player limps in EP. (I know this player raises his strong hands, so his limp indicates he's got the weaker part of his range)
A solid TAG limps along from HJ (he raises the top 20% of hands in this spot and limps along with the next 15% of hands, so I have a pretty good idea what his range looks like)
I have A
K
on BTN and raise for value. The blinds magically fold. 3 ways to the flop. Pot has 7.5SB before the rake.
4
4❤️5❤️
They both check to me, I bet
(I have the best hand often enough to bet for value - my equity is likely 33%+),
EP player raises, TAG folds.
(I know EP doesn't have many 4s his range because he likes to slowplay really strong hands and will take the x/c x/r line with trip 4s. He likes to x/r all flush draws, so he can have a lot of those. He x/r'es OESD too, so he can have 67s, but not 67o because he'd fold that pre. He'll also raise vulnerable made hands like 5x and over pairs that didn't raise pre flop like 66 and 77. Because I've got a read on this guy, I'm able to narrow his range a decent amount.)
T
(5.75BB)
EP bets, I call
(His bet means that he doesn't have a FD or SD because I know he has the bad habit of checking missed draws on the turn after x/r'ing them on the flop. Now I can narrow his range to 5x and 66, 77. I have 6 clean outs vs those hands. I need 6.3:1 to draw to my outs and am getting 6.75:1, so I can call profitability.)
A❤️
EP checks, I bet
(I bet for value because I've narrowed his range with the information I've received such that his most likely hands are ones I can beat. Easy value bet)
He calls and MHIG.
This is an over simplification of what my thought process is during a hand, but you get the basic idea.