So, just looking to see what everyone's line is in this situation.

I am playing $1/$2 NLH.

UTG+1 limps in, and so does Button and SB. I am in the BB with Jacks. I raise it $15. UTG+1 calls, Button ans SB fold.

Flop comes K24

I have the J in my hand. Pot is $34 I bet out $18, a little over half pot. UTG+1 folds.

While I won the hand, I'm looking to get critique on my line as I want to work on making the best possible decisions. Would you have checked the flop? Would you have bet more/less Pre flop or on the flop? Thanks!

A little more pre...I like flop bet.

How much Pre? What's your thought behind it? Just isolation, trying to get it down to heads up or take it down pre?

What are effective stacks? I think your sizing pre is fine. You don't want to take it down pre. You want a heads up or three way flop. With this flop, I think either bet or check is fine. But I lean toward a check especially being OOP. You aren't getting three streets, and with J there are two fewer turns that will ruin your hand.

Didn't follow this part completely. Can you elaborate?

3 limps to you, so I would make it $18, 5+1 for each caller and 1 for being OOP. You can make an argument that 15 and 18 isn't that big of a deal, but 13 into 21 is almost 2-1 IP while 16 into 24 is 1.5-1, which is quite a bit worse off. This way you are much more likely to be heads up to the flop that 4 way, which is a disaster OOP for big pairs.

AP, on the flop, we can charge for value or check for pot control. I think either have merits and we should be doing both a certain percentage of times, and for the 3 combos of QQ and JJ, we are more likely to pot control than the 3 combos of QQ and JJ without a heart. However, I would like to hold this thought for a moment and take a look at charging for value instead.

The biggest issue here that may cause us concern is definitely the K, in the case of flush draws, we definitely want to charge them, and with a board like this, we are probably not gonna go broke here against 44 and 22. The main question is, what combinations of K does villain have here. AK and KQ will most definitely put in a raise pre, and we heavily block KJ and even so that is quite the wide limp call from UTG+1, so this line is more likely to be KJs if we put KJ into villain's range, and they obviously can't have KJhh or diamonds, and depending on hero's other J, there might only be 1 KJs combo available. We can also put KT combos in but much like KJ, this is quite the wide limp call and we can largely discount this. All in all, Ks appear in our range much more than villain's range, so we should not be too scared here. If we charge value, we need to go for thin value, and the main hands we are looking for a call here might be 66-88 or hearts. In the case with 66-88, they can't call too big, and if we want to charge hearts, we also don't need too much to deny the 15% change they hit on specifically the turn. So all in all, if we want to go for value here and keep the villain's range as wide as possible, we could go with 30-40% pot instead of 50%+.

So now if we go back to a check for pure pot control, which combos of QQ and JJ do we select, because we just established that we should be mainly charging for value and occasionally go for pot control. So a good turn bluff when checked to a second time for the villain is a hand like maybe A4dd, a hand that caught a piece and has backdoor equity. In which case we want to deny part of that equity with a J/Qd. So for natural balance, we can opt for a check with specifically JJ/QQ in hd.

tl;dr, can go for check for pot control with specifically 1 combo of each JJ and QQ in hd, bet small for the rest.

Sure. Q or A turn isn't as much of a disaster since hero has J.