I'm having some issues statting out a badger Animal Companion for a 6th level Ranger in D&D 3.5 Can anyone provide step by step instructions that I can follow whenever I create an animal companion?

Specifically, I'm looking for things like:
 

1. Take the HD from the basic animal in the Monster Manual, then add additional HD based on the half the Ranger's level. These HD also add to Str...
    
2. Figure BAB based on....

For some reason, these rules always throw me for a loop and I always miss something.

I'm having some issues statting out a badger Animal Companion for a 6th level Ranger in D&D 3.5.

Can anyone provide step by step instructions that I can follow whenever I create an animal companion?

Specifically, I'm looking for things like:

1. Take the HD from the basic animal in the Monster Manual, then add additional HD based on the half the Ranger's level. These HD also add to Str...

2. Figure BAB based on....

For some reason, these rules always throw me for a loop and I always miss something.