Another rule you should follow.

Is there more then one form of contact available for that host. When I was doing reseller hosting I found alot of the times that hosts with email only contact didnt last very long. A rule of thumb I made for myself was this.

Does the host have a Phone number? If so does the area code match on the whois information ?
Does the host provide its' street address ? If so does it match on the whois information ?

Keep away from hosts' that have only 1 email address listed for contact