I find that once I get the regular straight fence at the proper angle
(a few degrees off parallel with the blade) it works well for cutting a
straight line. If your bandsaw came with a fence, or if you bought one
specifically for a bandsaw, or if you use a straight piece of leftover
lumber, it should be adjustable a few degrees either way.
I highly recommend a bandsaw book like "The Bandsaw Book" by Duginske -
lots of helpful background info and tips.
Good luck,
Andy