Watch a few tuyrkey hunting DVDs. Most of the major call makers offer instructional DVDs with a call.
***the following information my ellicit strong feelings from other turkey hunters***
1. (Best Bet to Start) Slate call. They are easy to learn and versatile. They come in a variety of surfaces. Slate/ceramic or crystal are good surfaces to start. Some calls have 3 or 4 different surfaces, allowing you to sound like different hens.
2. A box calls are easy to use, but may require a bit of care to maintain their tone.
3. Mouth calls are good, but require practice.
4. Push button yelpers are easy to use, but less versatile.