What is best practice for naming WebApps? Should each WebApp have its own apppool and identity or can they share?
Security boundaries should decide weather you choose to use seperate application pools to different web applications.
For example if you plan to use one web app for internet/extranet and another for intranet, it would be recommendable to use a seperate application pool for each web app.
Also be aware of the soft boundaries (aka Magic Numbers) with regards to application pools. They consume alot of RAM and seperating between web apps also have an overhead with regards to services etc.
Hence it is recommended not to exceed 10 application pools (depending on hardware and workload) http://technet.microsoft.com/en-us/library/cc262787.aspx#WebserverAppServer
Web applications are more fuzzy, but a reasonable number here is around 20 http://www.benjaminathawes.com/blog/Lists/Posts/Post.aspx?ID=18