1. What space are they offering?
2. What bandwidth are they offering
3. How many domain names can you host in one account?
4. How many emails accounts are allowed?
5. What’s the limit to send emails per hour?

For e-commerce sites the following features are a must:

6. Must be Fantastico enabled or equivalent Open Source
7. Allows more that ten Databases
8. Has SSL Secure server

I usually recommend two companies that have passed the test of time:
1. Blue Host
2. Think Host