If you took it easy during the marathon and ran it at least 90 seconds per mile slower than you could have run it and you don't have any lingering pain, then you should be OK to run another marathon in about 4-6 weeks after your marathon. If you really have your heart set on running another one a month later, you don't need to do another long run before the race. Take it easy for two weeks and then follow the two-week tapering schedule you did for the previous marathon. If it's more than four weeks, make sure you take it easy for at least two weeks, and then pick up with your marathon training schedule for the remaining weeks.
If you ran your marathon all-out, at your full potential, based on your current fitness level, it's best to wait another 4-6 months before racing another one. You would want to take at least three weeks to let your body recover (no hard workouts or really long runs) before you start another marathon training schedule. Ideally, runners really shouldn't run more than two marathons a year.
Also see:
What to Do After You Finish a Marathon
