Stoyan Stefanov has posted a few suggestions that you should probably ask your host-to-be before taking the plunge, making the commitment and entrusting your life to them (well, at least your data).
know choosing a hosting company is not easy, mainly because of all affiliate sites that publish fake reviews selling the host. Just like most other things, it's pretty hard to find unbiased reviews. So here's a list of questions to ask your future host-to-be, hopefully if they say YES to all, they have a pretty good shot at being decent.
While he admits that there are non-technical questions that should be asked too, he offers up some of his suggested technical ones to help weed things out quickly. Several are more general types (cron jobs, parking domains) but others are more PHP-related (using php_value, changing php.inis). Check out the post for more suggestions.