Depends what you're looking for; dedicated, VPS, or shared hosting. All three have different criteria when picking a reliable hosting.
If you're picking dedicated, don't pick a server that is an old model. Also, find out in which datacenter that server is located. If the datacenter has a good network to Europe, United States (and Asia, if that's your target audience), then you're good to go. Look for a hosting that gives at least 7-day money back guarantee without reason. During that period you can open up a few tickets and see how quick and informative their customer service is. The same counts for VPS and shared hosting.
For VPS, I would pick SSD (they're faster than HDD) and one that supports IPMI. For shared hosting, I wouldn't go with a large hosting company, because every ticket you open, they'll send you a link to a prewritten article on their website to solve your problem. It's too impersonal for my taste and not as effective as they think.