Ok, that makes sense and actually clears up a few things for me. But what I'm not sure of now is what hands give me what odds. Modifying your example above, what if the SB goes all in for a total 4000 chips. So a total pot 7k and 2k for me to call. So now I have only 7:2 or 3.5:1 odds. What hands are good to call with now? I think this is actually what I am more confused about and don't have the answer to.
EDIT: Thank-you to jimmym too. I think we were typing at the same time. And I actually never thought to consider pot odds when bluffing, it definitely something to consider. (And I actually have a drawing odds cheat sheet. It so helps with online poker when you have a very limited time to do math calculations in your head.)
