We are pretty close to going live with our new C5 site and I was wondering if someone could explain the "Speed Settings" in the Sitewide Settings page.

It says that Full page caching can dramatically lighten the load on your server and speed up your website. I'm all for that and we currently get about 4,000 unique visitors/day so anything that can lighten the load on the server sounds good. Can I get some advice on which setting to use? Currently it is set at Basic Caching - Disabled, Full Page Caching - Disabled. Do we want Full Page Caching Enabled if blocks allow it or Enabled in all cases?
And then, what is best for Full Page Cache Lifetime? Default, 0 minutes, Custom xx minutes or until manually cleared?

Thanks for your help.
John