Hosting is only half the picture.
If you are truly lost and building a business around a web site, kidnap or hire someone that knows about hosting.
A key consideration is management of your hosting platform. As you move up the service ladder, you gain more power and control. With this control comes more responsibilities, which may or may not be met by your hosting provider.
For example, I know of a business that moved a growing blogging operation from shared hosting to VPS, only to find out after a database failure that backing the VPS was his responsibility.
I highly recommend people lead with business requirements. Who's going to backup the data? Who's going to keep the application secure? How much money do we lose if the site goes down? How will server outages impact our client's impression of us?
There are a lot of business questions to answer before you even turn to application requirements.
You may find you have modest application requirements but significant business requirements.
For example, I have a client with 30-40 targeted domains with simple lead generation forms. You would think this could be on a shared reseller plan but they have 2 dedicated servers. One is a hot spare in another facility. Why?
The site serves lead gen pages for TV advertisements. The TV ads are expensive and not easy to pull in an instant. The last thing you want is to spend $10K on day's TV ad run and then have your site offline. So they spend according to business needs not technical ones.