You don't need bait to fish, just a fishing pole, the important thing is to fish in lower level zones until you get your fishing skill up. If you are new to fishing you cast your line, wait for the bobber to splash, then you right click it to "catch" the fish. Being a night elf I fished from Rut'Theran Village until I reached a skill level of 75. This provided the most "skill-ups" per cast to that level, then I moved to Darkshore for further skill-ups.