Ordered by importance in this order (1 being most important)
1. Uptime
2. Support/Reliability (Testimonials help!)
3. Web space/bandwidth
4. Price
A lot of the web hosts out there sell massive amounts of resources, thinking that their users will never use 90% of what they have allocated to them. This can make them a lot of money with users signing up thinking they have all these available resources. I have seen businesses do this, and they end folding rather quickly because their servers can't handle the stress/load which they allocate to users. Overselling is not a good thing! HostGator (Link:
HOSTGATOR WEB HOSTING - cPanel, Reseller, and Dedicated Website Hosting) is known for not overselling their resources, and now they have become of the best known web hosts in the world (gained over 34,000 clients in 1 year!). Make sure you take a look at their support/uptime rather than how much resources you can get.