It's almost always cheaper to buy your ground beef in packages of 3 lbs. or more. Then, when you get it home, you can divide it up into smaller packages. A kitchen scale is really handy for this, but you can divide it up into fairly even packages without one. For most recipes it's not going to matter if you're off a little one way or the other. I've only recently started using a scale.
A pound of hamburger fits nicely into a quart-size zipper bag. I've found that it works best to flatten each package before placing them into the freezer. The hamburger will freeze faster that way, and the packages stack neatly in the freezer. Additionally, when you're ready to use some of the hamburger, it will thaw faster, too.
I've started putting my hamburger into 1/2 lb. packages, since it's just my husband and me most of the time these days. If I need to cook for more people or make a larger recipe, I can easily take two packages out of the freezer at once. I bought two 3-lb. rolls of Ground Chuck at Walmart this week - because they'd marked it down to $5.94 (~$2/lb.) to sell it quickly, so I put 12 1/2 lb. packages in the freezer yesterday. That ought to do us for a while.