For each bottle, you'll want about 3-6 vanilla beans (depending on how fast you want it to turn into vanilla extract and also how strong you want it to turn out).
With a sharp knife, split the bean in half (I cut mine so they are open but still connected like a hot dog bun) and put into the jar.
Fill with vodka, close the jar and shake gently.
Tie on a label and put them away, shaking them every couple of days or weeks, until you're ready to hand them out as gifts!
Some people strain their vanilla before they give it as gifts so it looks clearer, but I really like the little flecks of vanilla beans for additional flavor and because I like the look of it in baked goods.
Also, the longer it sits, the better it'll get. My current bottle is about a year old (I just stuck an entire package of 30 beans in the whole bottle of vodka and keep it in my pantry) and it's fantastic.