Baby feet get cold really easily, so it's important to keep them covered. Besides baby socks are a really easy and inexpensive gift that's also stinkin' cute. Unfortunately, babies excel at kicking them off--usually within five minutes of having had them put on. But I have two pairs of socks I made for my little guy that stay on pretty reliably, and they both have cuffs.
The trick is to have a cuff that folds over the ribbing to prevent it from stretching out of shape. The easiest thing to do is to start the sock with the ribbing, follow it with a round of purling to create a crease where the cuff will fold, and then do stockinette for the same number of rounds as the ribbing. Once the sock is complete, fold the ribbing down into the cuff and tack it in place.
You can also start with the stockinette tube (or any other pattern stitch, for that matter), do a round of purling, and then do the ribbing. This way you don't have to sew anything, because the cuff folds out. You just have to do the cuff inside out.