I'm a late bloomer and didn't join a basement jam until I was 50 and I played my first show in a gigging band when I was 54, so I'm always the least experienced person I play with.
Usually by a lot. So I don't have the advantage of having learned when my brain was young and sponge-like and then had decades of experience to be able to just feel where we are in a song and create magic. For me, I find that I have to stay sharply focused on that balance between "being in the moment" while still paying close attention.
Some things that I've found help me:
- Pay attention to the structure of a song. Nothing I've ever played was one random measure after another, so there's always structure in the song. For example, a verse might be one or more repeats of the same progression, the bridge will be its own thing you play maybe a few times, and the choruses are generally all the same, etc.. Recognizing that, working on those patterns/progressions, and then working on the transitions between them helps me learn songs faster and also give me "signposts" that I can recognize when we're playing a song. Might not work for everyone, but it simplifies things for me because now I only have to learn a few relatively short passages and I'm 90% of the way there with a new song. Then it's just making sure I can put the parts together in the right order.
- A couple of guys in my gigging band do occasional backing vocals but I'm in on all backing vocals and our BL/singer also has me doing an increasing amount of lead vocals or sharing LV with her. Well, playing while singing is a lot harder for me (as it seems to be for a lot of us). But seeing the flow between lines in verses and in the chorus, hearing what word ended the line I last sang and remembering the next line that rhymes with it also helps me keep focused on what the next line is. Also, remembering that a verse is like a paragraph in a book, so seeing what that "paragraph" is saying helps me more easily see what the next line will be.
- I find it easier a lot easier to work on playing and vocals separately until I'm pretty comfortable with both. Then I start working on putting them together. For lead vocals, I sometimes make minor changes in the cadence or I sometimes slightly alter what I'm playing in order to get to the "that'll work" point quicker. Over time, I'll work on getting closer to playing it the right way. That won't work in a tribute band, but we're not a tribute band.
- Some things, like a signature line, need to be played right. So I focus on them first when they're in a song and I get to the "that'll work" point for the rest of it. Then, over time I work on getting the rest closer to the original. Some bands might not give you that flexibility but we're a bar band. It's OK.
- Maybe it's nerves? Some people might say have a drink or two before playing to loosen up, but I treat a gig like I'm working (I still have fun, but I'm there to put on a good show) and I don't drink when I'm at my day job. I want to have all my faculties so I drink only water. I also learned that I can channel that nervousness into focus. A little bit of nerves to go with the adrenaline isn't necessarily a bad thing.
- And, seriously, practice helps. I do NOT play every song perfectly. But, by regularly practicing our gigging material, I get more comfortable playing them live. Also, NEVER stop and re-start a song when you're practicing. If you make a mistake, recover as best you can and keep going. That will help a lot when you're in front an audience. It will also help you work on that line between focus and being in the moment so it will get easier to maintain it while playing live.
- Realize that no one else out there is perfect, either, and sometimes those bits of truly inspired playing you hear are accidents. Even the so-called gods are actually mere mortals. And, if you mask your disgust at yourself, few people will notice the mistakes you made. Even your bandmates!
Sorry for the long post but, as a relative newbie who's working through something similar, I figured I could pass along things I'm doing that work for me.