I've been leading a group of about 25 men and women carollers for about 10 years now, with myself on guitar. I stand facing the group, and tell them to make sure they all follow me, rather than trying to blend in with the group facing out.

I have a Martin HD28, which has lots of boomy sound and can be heard very well, and I use a flatpick. Boom-chuck is very important, as are bass runs to cue them as to when to come in and when the next line will start. I sing along with them, and face the section whose part is coming in, as would a choral director. I also tend to bounce up and down with the beat. I do this anyway, but it really helps keep the group's timing together. Visual cues like a head bobbing, guitar dipping from left to right, whatever it takes to make sure all singers know where '1' is.

Over the years, a couple of other guitarists have joined me. I have them line up with the singers, facing me, because only one person can actually lead. I put one on either end of the singers, which helps spread the accompaniment around.

The other thing that helps is to have a little songbook with lyrics and/or music to pass out to all the singers. Then I can call out a page number, and we're all "on the same page."

It's really fun, and very gratifying, so keep trying.