I had a 
purple Sphero combination lock from 
Masterlock to secure my storage area in my apartment and guess what, I had lost the code for it. Ooops !! And I had been running around all over the apartment to get it in vain. And then I tried Masterlock website and they tell me to do a 
bunch of stuff to get the code back. And then 
Google came to my rescue. And so did 
digg's post on 
how to pick a combination lock. And finally, this 
wonderful source came to my rescue. Armed with a 
combination lock spreadsheet and my friend's help, in a few minutes try, Bingo !! The code was cracked.
In this method, you would have to try only a maximum of 100 combinations, and if you had some sense of what numbers  you might have had on your original lock, it is even easier.  The most suprising thing is that all the codes are either odd or even digits (from 0 to 39).  
All Master lock have the same pattern of the codes:
The lock has a dial with 40 calibration marks numbered 0 to 39.  A combination consists of 3 of these numbers, for example:  15-25-7.  To open the lock, the following steps are taken: - turn the dial clockwise 2 full turns 
- stop at the first number of the combination 
- turn the dial counter-clockwise 1 full turn 
- continue turning counter-clockwise until the 2nd number is reached 
- turn the dial clockwise again until the 3rd number is reached 
- pull the shank and the lock will open
Source