Standard Spot I still get confused about

[Downtown]

Ok, so this is def a leak in my Holdem game. Been in the situation a few times and I end up 80% of the time folding. I just feel like its so weak.

Anyway, heres the situation. Its a full ring game, doesnt matter whether cash or tourny. Mid position opens, I decide to flat behind with a hand like 99/1010/JJ.

Flop comes 368 or something like that. Maybe 2 of the same suit.

Now the Opening raiser checks, I decide to protect my over pair and bet. I get re raised.

This situation happens alot, I know I have completely under repped my hand and thats obv on purpose.

Would someone discuss the ultimate strategy for this spot. What % Should I be 3 betting these hands pre? What do we think about betting the flop? What hands do players c/r in these spots?

[TommyGunne]

3betting preflop is hugely dependent on villain. Vs some of the nitty guys, I don't 3b any of them. Most live people just never fold to 3bets, so you could probably 3b JJ anyway despite their tight opening ranges. They'd want to be in a bit later position for me to be wanting to 3b TT, and it would have to be exceptionally rare circumstances for me to want to 3b 99.

Betting the flop when checked to is obv fine, and what you do to the c/r depends hugely on villain. Can't do too much better than that, cos there are some guys that this would be a snap fold against, and some you'd try felt TT+ anyway.

[BobSloane]

Now the Opening raiser checks, I decide to protect my over pair and bet. I get re raised.

This situation happens alot, I know I have completely under repped my hand and thats obv on purpose.

If its happening a lot then checking back seems like the best default if you're never betting and calling. You dont have much to protect against. (silly)players do c/r with flopped draws because they dont want to bet and get called and not know what to do on the turn. But by bet/folding your hand you do the opposite of protecting against a draw. You anti-protect if anything!
Sometimes people will c/r with overpairs too in which case you are valuetowning yourself in a hand where you have 2 outs to improve to stack him where you could have maybe called a turn bet and decided on the river. If he has c/raised with a set its obv the same as an overpair vs your hand.
So all you are really protecting against by your flop bet is overcards - which are only going to pair up on the turn 1/7 of the time anyway so i'd take those odds and gamble check back @6-1 and maybe pick up a bluff later in the hand, fold later in the hand or bet if he checks the turn

[KKrrusher33]

by default i am always betting for protection in said case i.e. readless v an unknown. if i m c/r i will let it go mostly. kinda sucks coz alot of the time u will be folding best hand against a donk who figures u would have 3-bet him pre 100% of the time with 99+ and thinks his small pair or pichaa cards is really the nuts vs ur standard take-the-pot-away-with-air-bet and the other ones who like to c/r their flush and straight draws but u just havent evidence just yet for that. if they c/minr its just more annoying. i fold til i build a better idea of their ranges, tendencies and playing style (or more hands on him for stats if online)