1/3 table, first 1/2 hour so no real reads. Assume he is standard ABC player.

Guy raises to $10 early position, I'm next with JJ. I just flat, another guy calls.

Flop K 8 4 rainbow. All check.
Turn 10. PF raiser bets $20. I call.
River x, under a J. Guy bets $25.

Should I have 3 bet him pre? What to do on the river?

Assuming 100bb stacks, I'm cool with just flatting preflop. There's no significant dead money in the pot and we are facing an EP raiser. If there had been a few calls before us then there is a better argument for going after the dead money.

I would probably bet the flop when checked to. The check indicates perhaps the raiser simply has A high, so we're pretty cool with taking this down now with our vulnerable hand if it is best. With ~$30 in the pot I'd probably bet just $15 and evaluate from there.

Turn is really opponent dependent. If he's bluffier versus flop weakness then we might have to wager a call here. Otherwise, once most Ax players wave the flag on the flop they are unlikely to change their mind on the turn (although some hands did pick up a gutshot or hit a pair with a T).

We're getting ok odds on the river of almost 3:1. But do we really think he's betting a T or barrelling a busted gutshot for a small amount that is easily callable? Again, really opponent dependent.

In the end, the opponent is assumed to be a standard ABC opponent, which is why I'd lean towards betting flop myself and folding turn/river (with turn being close) as played.

GcluelessNLnoobG

These are all decisions where either option is OK.

Preflop knowing stack sizes makes a difference and even after half an hour you should have some read on how aggressive the table is in general. For the most part both flatting and raising is fine. Flop you can bet $15 after preflop raiser checks but checking is fine also.

Turn I favor a call but folding is OK. Villain checked flop but is still betting into multiple opponents on turn. This is where having a better read on villain really matters. Depending on opponent this could be anything from an easy fold to mandatory call.

River is meh. Getting decent odds calling can't be bad given your hand but knowing something about how villain bets could make this decision much easier.

I think a 3bet preflop is superior, but calling is fine some of the time, imo.

anything else to go off of will lean me whichever direction pre flop.

what race, age, sex, clothes, etc all going to be needed here.

The worse my racist prejudice views think he is the more likely I'm raising here.

So I ended up calling and he shows 88 for a set. Stack sizes were about $150-200 each, can't remember exactly.

30's Asian guy, but there's tons of Asians in my city. Didn't seem spewy or out of line, and as I had just sat down recently decided to be more conservative and just call pre and check call.

Lol yep.