I have just recently learned (although I used to fold mostly anyway) that calling a 3bet with KJ is a horrible move. You are so incredibly behind it's not even funny. Any broadway cards he is holding completely dominates yours.

If you want to call a 3bet in position, you *MUST* have QQ+ or lower suited-connectors like 78s. I am on the fence wondering if it's worth calling with low pp's but I've had moderate success doing it if I am in position.