Regarding “tightness” you should be able to pluck the blade
and hear a hummm (similar to a musical instrument) if you
hear a very dull sound, your blade isn’t tight enough!
Great advice… good descriptions! I would just like to add
that I think the sound you should get when plucking a newly
installed place is more like a “plink” than a “humm”. 
Also, when sawing sheet under normal circumstances, do your best
to always keep your blade perfectly vertical. It shouldn’t tilt
forward into the cut, or lean left otr right. When sawing tight
curves, turns, etc, don’t be so concerned about forward motion.
Take a few extra strokes and make your turn in place.
If your blade does bind, it generally means the metal and the
blade are thinking two different things. Usually the metal will
win, and the blade will break. What I’ll do in this situation is
release the metal from my other hand, and let the blade relax so
that the metal is in proper alignment with the blade. I can
usually continue cutting from that point with no problem.
Hope this makes sense,
Dave Sebaste
Sebaste Studio
Charlotte, NC
dave@sebaste.com