I'm a relative newbie to live performing, so I'm still winding my way through the ins and outs of getting on stage.
When I'm practicing at home (I'm a solo player), I usually sit on my comfy sofa, and I mostly play unplugged. Sometimes I use an amp, but my focus is generally on technique, making sure I have the chords, leads and singing in tune with the music.
But it all changes when I take the stage. For example, last night I played at a small venue (seats about 60) which has its own in-house sound system. A very nice stage manager handles the mics, cables, stands, seats, etc. So, because I play seated at home, I chose a stool, and then plugged in. Youch! My guitar was set too high, so I had to tone it down. OK, no problem, and quickly set to volume and tone I liked. Then I started. About two choruses into my first song, I realized I couldn't hear myself! Yes, I was singing into a microphone, but there was no on-stage monitor, and I actually couldn't hear the words I was singing. Worse, I couldn't tell whether I was singing in tune or not.
Given time constraints, I couldn't stop and ask the sound guy to work with me, so I muddled through my set, all the time knowing that I was likely missing notes (I'm not a trained vocalist!).
Forewarned is forearmed. The next time I go, how do work with the sound guy before I'm given the "go" signal?