Navigating Cisco's documentation is a quite easy. The IOS documentation set consists of many volumes of "books". They must be quite useful to some one otherwise why would they exist?
IOS Software Documentation
To me only the following sections are really important.
Configuration Guides - This set of documents gives you a list of all generic features and how to configure them.
Command Reference - If you want to get further details about a command, what it does or what its options are use these documents. This is not the master command reference!
Feature Guide - This shows all the new features being added to the image and how to configure them. Eventually this information will be ported over to a section in the Configuration Guide.
Master Command Reference - This is the nirvana of all documents. Its lists all the command across all the images. If you are utterly lost, get the PDF version(s) of this document and search it! I think it should have a more prominent place on the Cisco web. So if you happen to control this documents position then "make it so, Number One".
I could just list a link to all these documents but the real point of this note is show to you can navigate to each of these documents manually. So the only link I present you with is the link to the Cisco Website: http://www.cisco.com.
So to start with go to Cisco's Website. Click on Support and then click on All Products:
You will be presented with the view below. If you are an old techie, this view is equivalent to the old UniverCD.
Click Product -> Cisco IOS & NX-OS Software -> Cisco IOS
Then pick your IOS version and train. In this case I'm going for 12.4T. Then click on Configure on the left and Configuration Guide on the right.
You will then get the list of all the generic features and how you can configure them.
If you click on Reference Guides on the left and then Command Reference you will be given a similar list of all the documents.
To get to the Feature Guides click on Configure and then Features Guides (see image two above).
The Master Command Reference can be found by clicking on the Master Index.