I also had this dilema of adding vanilla for the first time. I was adding it to a breakfast stout. The method that sounded the best to me from researching many web sites and recipies was to start with a quality bean (see other recommendations in thread), split the bean to expose the seeds, cut the bean(s) in 1-1.5" pieces and soak in a small jar with just enough QUALITY 80 proof Vodka to cover the bean(s) pieces. Remember this will be in your beer so don't be tempted to use the cheap stuff many of us sanitize with! The Vodka serves to sanitize the bean and to draw the goodness out of it just like when someone makes real vanilla extract. You can let this soak for up to 6 months or more, but 2-4 weeks is plenty for what we are doing, this plus the time in the 2ndry will bring out the best of the bean(s). Place the beans and vodka in the secondary and enjoy! Sorry, but I have no help on quantity since that depends on what you want.