Vanilla beans, 3-5 or more for a larger jar (I use Madagascar vanilla beans)
8 oz. Alcohol of choice (vodka has the most neutral flavor and an expensive vodka is not needed. Just a mid-grade one will do. Or get adventurous and use bourbon, brandy, or rum. These yield a stronger flavor.)
Clean jar or bottle
Sharp knife and cutting board

Split the vanilla beans, leaving the ends intact to expose the inside or chop into pieces if you like.
Place in clean jar or bottle.
Pour alcohol over beans making sure they are completely submerged.
Place airtight lid on container and give a little shake.
Let sit for a month in cool, dark place. You can shake it from time to time. You can use more beans to speed the process. Or allow it to sit for 2 months for stronger flavor.
You can use a coffee filter to strain your finished extract if you want a clear vanilla. I, however, like the little vanilla bits in there.
Top off the bottle as you use the extract to get all that flavor out.
I discard my beans after 3 or 4 refills (adding a new bean here and there) because those beans will eventually lose their flavor infusing ability.