Reliability: Reliability is very important since this will determine the availablitiy of your website. I consider reliability to be of utmost importance. The term "reliability" is a bit general but it encompasses many options. In this case, my focus is on down-time. If the host you select is always "down" or "slow" then it can affect your business. Review carefully the uptime percentage the host has listed on their website. Some hosts will display the uptime status of their servers.
Pricing: Sacrificing a few dollars for better quality service is usually worth it in the long run. Carefully go over all the pricing options available with the hosts you've reviewed. Compare their pricing and plans, and based on that you can make an informed decision.
Support: It goes without saying that legitimate around the clock support is preferred. You should ensure that the web host you select is easily accessible via email, telephone or live chat, 24 hours a day. Many hosts advertise this, but do not honor it. Before registering with any host, always send a test email first to their support department to see how quickly they respond to your query. You could also call the host outside of normal business hours to see if they really do provide suport around the clock. This will give you a good indication of what to expect if you should decide to host with the company.
Features: When selecting a host, always review the features they offer. You should never "assume" that the host provides all the features you are looking for. Carefully read the list of hosting plan features. If there is a particular feature you require, and it's not listed, then send a support query inquiring if the feature is available.
Reviews: Do your due diligence, and search for reviews on the hosting company. There are many websites that offer in depth reviews of hosting companies. Another good idea is to conduct a search on Google regarding the company to find feedback from current or past customers. You'll also find that many hosts have an open support forum format. Browse their support forums to get an idea of what their current customers are saying about the service being offered.
Overall, the key to selecting a web hosting company is to always do the necessary research, to ensure the company offers all that you need. Review feedback, and weigh the pros and cons, and you'll then be making an informed decision rather than a blind one.