What Is the Web Host's Reputation?
The best thing you can do when shopping for a web host, other than make sure the site is running *nix, is to check a site's reputation. Finding that you're at the wrong site can cost you time, trouble, and lost customers, so this is time and effort well spent. Although what you can do to discover this in advance is somewhat limited, it's due diligence, and you really should do it.
Start by searching at Google for review sites, and visit them to see what current and former users have to say about prospective hosting providers. Take good reviews with a grain of salt. Ever since user reviews became popular, unethical businesses have loaded up online review sites with positive comments. Contact the people who have the most interesting things to saygood and bad.
Uptime also is important. Search under the name of your potential web hoster at Netcraft under "What's That Site Running?". The longer a site's uptime is, the better.
If you're new to this, one good place to discover the basics of setting up virtual web hosting is the article "Becoming Master of Your domain.com."