The first part of this is an extremely broad question and the answer depends greatly on the species of salamander. All salamanders require moisture and shun extreme cold. In Alabama, late winter and early spring are likely to be the times to find the widest variety of salamanders. As a rule, salamanders are mainly nocturnal, although newts may be abroad in daylight. During the day, most terrestrial salamanders will be hiding under logs, boards, and other shelters. They don't move very fast, and to catch them all you need to do is pick them up. It's best to use latex gloves to prevent your skin oils from getting on the salamanders, and be sure to keep them moist while you're handling them.
You should study the habits and habitats of the salamanders in your area so you'll know better where and when to look for them. The ZipGuide feature on our site will give you a good start.