As mention by franklinn, it all depends on what your site is. If you are a small business or med sized business, usually a shared hosting plan is more than sufficient to suite your needs. However if you are a large networking platform or a popular blog/entertainment site you will want to look in the realm of VPS (virtual private server) or a dedicated server, which can handle a high amount of traffic.
My recommendations: I use heytommy.ca for my shared hosting, they have reliable service and overall I haven't had any downtime with them.
For bigger applications I use dedicated servers from 1and1.com. They work quite well too and only recently have I had some troubles with billing, but again they have good support and solved it for me.
Hope that helps you, cheers!