As a novice worker but experienced bread-baker, I agree with the
sawing wood/slicing bread analogy. They're two very similar skills.
One thing I always keep in mind when slicing bread is to hold the
knife the way I would a saw. That is, with my index finger extended
and not curled underneath the handle. I think this helps you guide
the knife better. Also, as others have mentioned, let the knife do
the work; don't force or otherwise over-pressure it.
One other thing to remember, though, is that most bread knives are
serrated. The serrations, I think, do have a tendency to cause the
knife to pull to one side or the other. (Sorry, I can't remember if
it's towards the serrated side or away from it.) You do need to
apply slight pressure to compensate for this tendency.
-Brian