Problems happen and no technology, no hardware or software, is fault free.
“If General Motors had developed technology like Microsoft, we would all be driving cars that would crash twice a day for no reason whatsoever.”General Motors Press Release
More than anything else, making sure that your hosting provider has a robust support process and a skilled team of system administrators and engineers is a must.
Of course, everyone will tell you that they have these things, so you’re either going to have to dig around for information online or get a recommendation from somebody. Personally, I prefer a word-of-mouth recommendation from somebody that I trust over anonymous content on “trust” and “ratings” websites.
Most good hosting companies have a “status” page on their website that lets customers know if there are problems with any of their systems.
If the hosting company that you are looking at doesn’t have one – bump them off the list. If they do have one – monitor it for a few days. Check to see if there are problems and, if there are, how quickly are they resolved? How good is the communication with customers when the problem is going on?
It’s also worth looking at the hosting company’s social media, in particular their Twitter feed; this is an easy way to find more historic information on problems that have occurred. Keep in mind that some savvy companies have a separate Twitter account for support and status announcements, so make sure you’re looking at the right one if you’re doing a little research.