I've been coding and configuring Salesforce for about 2 years. Most of that two years has involved custom objects and making custom apps and user interfaces.
I've realized that I don't actually know how to use Salesforce, in its pure vanilla form.
Let me use this analogy to help me explain my situation:
Many of us know how to drive a car, be a driver, but few us can actually customize our vehicle, mechanic: go under the hood to fix/upgrade something, body work, new paint job, change breaks, etc.
Basically, I'm a mechanic of Salesforce, but I'm not a good driver of Salesforce.
How to do I become a better driver? What resource is there that explains how to "drive" Salesforce?