It depends really on how old the games are you want to play. In most cases, just install the game as normal and play. Some older games may require updates, like Diablo 2 or Sims 2, but most should work fine on Vista x64 without any problems.
In the rare instance that you do have problems, you could always try compatibility mode, and if it's a really old game, download the free Microsoft Virtual PC 2007, install XP on it, and run the game in a virtual pc environment. I haven't had to do this for a while, but it may help you.