There are two things that are important to consider:
>Brake width. The bindings should be pretty close in width to the waist of your ski (the narrow middle section of the ski). Evo recommends a binding that is equal or up to 15mm wider. If you have to, you can go a few mm narrower and bend them, but it's not ideal.
>DIN. First, calculate your DIN using a DIN chart. Then find a binding with your DIN around the middle. For example, if your DIN is 6, you want a binding with a range of something like 3-12. You do NOT want a binding with a range of 1-6, or 6-16, or something like that. It's best to have your DIN around the middle of the binding, not the highest or lowest it can go.
There are specialized bindings such as AT (alpine touring), etc, but you don't have to worry about that. Just get some standard bindings.