Hey Frank,

When I'm recording, I always make sure to include a count in, as this really helps aligning tracks later. If I line up the beats of the count in and everything else is at the same tempo, it all just falls into place.

If there's no count-in, but everything is still at the same tempo, I would look for a unique moment in the track, perhaps one with a clear spike in the audio waveform, some silence on either side, or a unique sound that only happens once. It has to be a moment that is clearly defined in both the vocal and backing track. Then once that moment is perfectly lined up everything else will be too as long as they're the same tempo.