Hello!
Well, one trick I always used is this:
I used Audacity, and cut the sound off right at the end so that it would go back--but it would sound weird, wouldn't it? If you had reverberation or something that suddenly cut out, it wouldn't sound natural at all.
so, I simply took the REVERB that I cut off the end, started a new track, and pasted the reverb right at the beginning along with the first track. that way, the first time the song starts, it sounds a bit more explosive, and then after that, it just sounds seamless.
Hope that could help...
www.garageband.com/artist/hamilton