1. Understand the differing types of hosts
shared, collocated, unmanaged dedicated, and managed dedicated. Is your site brand new with little traffic? In the event your site is a newer domain, you won't need the raw power of a dedicated server unless your site is resource intensive which can include: streaming, video's, proxies and even linking to videos as well can cause a high load on Apache and the CPU(s).
2. Go for stability, not just size
Just because the host if offering you unmetered and unlimited space, doesn't mean you should soley base your decision on that. What good is that account to you when your site is down or the server is overloaded? Research how long the hosting business has been in operation. See if they have recently changed ownership, and if they show positive cash flow.
3. The possession of fully redundant data centers
If you are considering doing business with a smaller hosting vendor, ensure that they have adequate power and connectivity capabilities. Inquire as to the number of lines the facility has. Do they possess an on-site generator? Does the generator receive regular checks and maintenance? What is the average utilization of the connections available?