queen trade?

Do you trade your queens if you see you can go up the exchange?  I've been doing a lot of tactic lately and notice that anytime I can go up the exchange by trading queen's I fail the question. 

So my question has to do with in game situtations if you can go up the exchange do you trade and if so how much do you need to be up?  In the openning , middle and endgame I realize the answer will change so please feel free to help out by giving multiple answers... 

Thanks

I always thought it depended on how well both the queens are positioned, if it will destroy pawn structure, open up the king, etc. I don't really like queens anyways, so I'll trade in most circumstances.

if you are in the middle of a attack you shouldn't trade queens as your attack might disappear.

I was playing a game and I was up material so I thought I had to trade down as much as possible. After I traded queen I had no attack.

but on the other hand if your opponent has an attack against you it might help to trade queens as his attack may disappear.