That's very board, maybe narrow it down some? I can spend all day talking about tubular locks and how to defeat them.
About the first thing you should know is that they come in a variety of pin arrangements.
These include:
Seven-Pin Center
Seven-Pin Right Offset
Seven-Pin Left Offset
Eight-Pin Center
These will account for about 90% of the tubular locks out there these days. These are very easy to identify. Count the pins, and take note of their position. Offset left will have no pin at the 1 O'Clock position, offset right will have no pin at the 11 O'Clock position. Eight and seven pin center will be centered, you just have to count the pin stacks.
Then you also have ten and eleven pins, ACE II's, rectangular keyways (Tubar), smaller bores, etc.
The most basic of basic picks will allow you to pick all seven pin varieties. If you want more, then you'll have to get more specific picks in different configurations.
Describing how to pick one would take ages, so I hope you at least have a basic understanding of how they work, I'll be glad to give you some pointers but if you want a detailed description on how to pick them, you're going to have to wait till tomorrow night (as it is a bit late).  | 
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