I got my barrels from a local distilling company.
Different methods for barrel aging, but the one I prefer is throw caution to wind. I pull the bung and purge with CO2 and then rack to the barrel. When I put my bung back in I first drill a hole through it to fit a hard spile, this will allow you to sample the beer as it ages and allow you to determine when it is ready.
I have aged them for a minimum of 3 weeks and have gone up to 13 months. I then rack it to kegs (Sanke converted Hoff Stevens)using and old homebrew pump and then throw some head pressure on them to carbonate. Allow the beer to sit in the kegs for a few more weeks if you can.
I do this with my Oatmeal Stout and it turns out great. Picks up some really neat flavors from the barrel (Vanilla), the bourbon as well as some of the oxidative notes like raisin/plums.