On memorizing, a trick I heard from Michael Cooney:
Learn the song backwards!
Start with the last verse, then sing the last two, then the last three, etc.
The part that gets repeated the most gets remembered the easiest.
Make the later verses the most-repeated, so when you get "into" the song, the parts you usually would have trouble with -- the later verses -- will be the easy verses, since you've repeated them the most.
It's artificial as hell, and hard to stick to as a practice, but it works.