Thanks guys for the great tips.

I'm currently on FareCompare checking all possibilities.
I chose StarAlliance as I guess not only Lufthansa can give me points.
So my options are to go to Europe or Alaska (never been) or Venezuela.
The price it shows is cheaper than when checking via kayak.
Is there any way to buy there?
Also how do you make sure that you'll collect the number of miles as shown?
(I guess it depends on a booking class).
Asking because recently flew JFK-SFO-JFK with UA and one way collected 2,572 (V) but the way back 1,286 (W). Ticket bought via kayak(orbitz).

I know that it may sound lame for you, but I'm a newbie.

Thanks.