I actually started with solo stuff before getting bands together. To be honest, I used to find solo gigs a lot easier to do - everything under my control :lol:
Yeah, with a band, there's more of you, you feel less alone. But solo, it's all your responsibility. If it fails, it feels just as bad as it does with a band. But if you win, it's ALL yours! :D
I wish I could tell you how I know all the lyrics, I just do. 38th has got a good point though - if you get hold of first lines of verses/sections, the rest kind of follows. I found lyric sheets actually disabled that. I never used them in gigs, but I would in a rehearsal if it was new song. If I was relying on a lyric sheet, I'd stop paying attention to it when I knew what was next, then, for a dodgy section, even though I actually "knew" what came next, I'd end up getting lost!
What I learnt to do was put the lyrics over on the chair at the side after the first rehearsal - I could read it before or after run-through. The band would go "you keep f*cking up the lyrics, why don't get the sheet where you can see it while you're singing?" ... I'd go "We're rehearsing, I'm learning to sing it without the sheet..." ... by the end of the second or third rehearsal I wouldn't need the sheet at all. And some of them I could still sing to you now 30 years later!
Live, in front of an audience, when it goes, just sing anything. Even "I seem to have forgotten the words" to the tune you're singing. It kind of helps if you're a lyricist yourself - you feel more confident that you could probably write some more on the night if you can't remember the original. In the early 80s, my sound engineer, a big Motorhead fan, used to point out that Lemmy often got the lyrics wrong live, but they always made sense. Basically you learn what the thing's meant to be about, and tell the story, if it's different each time, who cares? :lol: (obviously, changing the hook/title ain't too hot - but you rarely forget those).
EDIT: I forgot to say Good Luck!!
Sort everything that you can before you walk on. Try to get acclimatised to whatever it feels like (monitors, vibe from the room, etc) as soon as possible - and accept it as it is... then just start enjoying yourself... the audience picks up on your enjoyment, they feed you back, you feel better and enjoy it more.
All this applies to playing in a band as well - but solo you're more out on limb... AND you're the only thing that the audience has to watch and listen to. So it's really important that you feel good and entertain them asap - they're on your side when you walk on, but if you don't engage them you'll lose them, and it's a very lonely 30 minutes or whatever... (especially when you find you can hear and follow their conversations over your songs!!)