I've always found them hit and miss, but lately they are frankly appalling. If they didn't have such good SPs I'd happily give up using them. I've missed a few opportunities because they are so slow to respond.
In terms of "tricks", I find that the fewer messages exchanged, the more likely it is to work out, so if you can get you entire request (who, what where, when) in a single message you might just get a confirmation back. any sort of dialogue tends to just fizzle out.