For a deep and rich home made extract, we like using six or seven LAFAZA Grade B vanilla beans for every 12 ounces of alcohol.
To make your own vanilla extract, spilt five or six vanilla pods lengthwise, leaving the top half of inch of the pod connected. Place the split beans in a clean glass container, and add about 12 ounces of good quality vodka or rum. Close the container and let it sit in a cool, dark place for one month (for rum) or three to four months (for vodka). You should gently shake the bottle every week or so. The longer you can allow the mixture to soak, the more rich the vanilla flavor.
You can also use brandy to make your extract. In this case, follow the steps above, but allow them to steep in the brandy for two to three months. Try making your own “vanilla sampler,” trying different types of alcohol bases to see which you like best.