Loosing Mosters to Sets

Could some one give me some advice on how to avoid loosing lots of money to opposition players hitting their sets. Is there specific betting peflop play that makes it unfrofitable for players to set mine?

If by "monsters" you mean strong pre-flop hands, then the only advice I can give you is to adjust your post-flop play. If you have aces but are forced into seeing a flop, you have to realize their value has been decreased. Although it is likely you're still good, if your opponent is willing to put his stack on the line on the flop then it is unlikely your hand is any good. This is assuming the stacks in question are deep. I am very aggressive with my premium pocket pairs on the flop but you can't be willing to recklessly go all-in just because you have a hard time letting go. It's frustrating to not get it all-in pre-flop and then be forced to fold but you can lose a lot of money with that mindset.

I am talking about large pairs, AA, KK, QQ. I got caught out with AA. The villan raised (UTG) 6 and I reraised 30, he called. We both had a stack of about 250. Would I have been better to raise to 15% - 20% of his stack to making set mining unprofitable. Of couse I still want to get a caller every now and then.

TBH its gonna happen.

You did the right thing.
3-bet and if they call with smaller pairs everytime thats a winning play for you.

Thanks for the advice.

My mistake - I think you're actually referring to OP not releasing his big pair in the face of resistance and not villian...sorry!

Yes, knowing when to lay down Aces or Kings etc is a disciplined skill and should be fairly easy! I say fairly, as it hurts everytime. Generally speaking if you get raised on the flop you need to seriously consider how good your one pair is now, on a draw KQT flop with two suits you could be in a lot of trouble. This board will hit your oppionenst range with all manner of 2 pairs, sets, flush and straight draws.