[vantilburg]

One handin's hated on by most, mainly because in 5 weeks a new spread player could beat someone who's been playing using one hand for half a year. It's hard to stick with, and the most efficient way to play would be using spread, but if you're still undaunted, there are a few tricks.
8 hour gave his general approach, but there are other methods - mainly involving up/down trills or streams relying heavily on those keys. I use both my index and middle finger for the down arrow, depending on the patterns. Left/down trills and slow up/down trills I use my middle finger for the down key - but for faster up/down trills I use my index.
Bynary Fission (another great example of one handed prowess) uses 8 hour's method of relying solely on the middle finger for up and down. However he uses the index finger for up/down doubles. Korny (well-known one hander) would use the number pad, effectively using four fingers one handed - index on 4, middle on 8, ring on 6, and thumb I believe on 0 - someone correct me on this.
Korny's method is probably the fastest, utilizing four fingers, but it's certainly more awkward and will take a while to get used to.
For songs to start off with, I'd suggest basically any song difficulty 1-5 not stepped by synth.

Christ what a text block; I slimmed that down, too.