One of my tricks, so that I can depend on my fingers to get the notes right while I concentrate on the feel I want to get across, is to play the tune as fast as I possibly can - even slow airs. It seems to help program the muscle memory and makes it much easier to play a difficult piece at a moderate tempo.
(This may not be much help if you're working on a reel that needs to go 90mph!
)
The other tip on learning new tunes is to start at the END of the tune. Master the last phrase, then work backwards towards the first phrase. (This is easier to do if you're learning from music.) This way there is always a little positive feeling from finishing well, instead of having to stop where you get bogged down.