An important part of internet is web hosting. Web hosting seems a small problem in the internet because there are many companies that offer web hosting at cheap prices. But if you choose a fake company or a low reputation one you may be in problem. For example you can loose all your data and work, databases, design, mails, and can cause very big problems. I personally recommend a big company because they are always trust and offer great support. A small company is usually not very impressive about their support and sometimes they even don`t know how to resolve your problem.
If you have big sites, with lots of unique visitors (over 100k/month) i recommend to use a VPS server to host your sites or even a dedicated server because they are faster, bigger uptime and they are very fast.
It is very important to look at the things they offer, and what they don`t. Many big companies have unlimited space and bandwidth. You might look at number of database that they offer because if you host more sites, you might need lot of database slots. If the host has a Site Builder add-on or a free included one it is good because help new ones in this domain to build a proffesional site.