What art most important features to look for in a web host?

I'm new to web design, and in the process of trying to find a good web hosting. I'll have a lot of videos and photos on my site, and wondered what kind of features are most important to me to be looking at when searching for web hosting. Some servers are faster than others? If so, what are the fastest? And it's better to go with a Windows or Linux? There are other important features I look for? Thanks in advance for any suggestions!