The last thing you want to think about having finished a marathon is what you are going to do next in terms of running, most people just think about what bar they’re heading to that evening! There is nothing wrong with a few celebratory drinks having done your marathon, however I would recommend drinking some fluids before hitting the town, your body will thank you for it the following day.
Immediately following your marathon
If you only drink one thing once you finish the marathon, make sure it is a protein shake, milk, or some form of protein. This will help repair the muscles that have been damaged during the race. The quicker you get that process started the quicker you will find your recovery will be.
The day after your marathon
Once you have got the evening after your race out the way, the following day you might find your movements are slightly restricted from painful legs. As much as you don't want to, I would suggest just going for a walk and keeping the legs moving, not too much - but just enough so you get the blood moving and flush the legs out following the race. If you can, it is a good idea to get a massage as this will really help the recovery process.
Gentle exercise initially
In the 2-4 days following the marathon there is no need to do hard exercise, gentle walking, light stretching and even a bike ride can help. You don't want to jump straight back into running the amount you were running before the marathon, take your time and build up slowly. Even if you left it to 2-3 weeks since your race before returning, then you won't have lost too much fitness, and therefore there is no need to rush to start training again.
Address those niggles
Once you have started running and got rid of the aches and pains you should start thinking about what to do next. I can't stress enough to make sure there are no niggles lingering from the marathon, and if there are, to get these sorted before running again. If you don't get these little issues sorted they can lead to much greater injuries, and even more time off running.
Analyse your marathon
If you are thinking about doing another marathon then I would take a step back first and look at the training you did leading up to the last one, what worked and what didn't. How did you feel in the marathon? Obviously there was a point you struggled, however if you faded really badly over the last 5-10km than perhaps you weren't strong enough.
Limit your number of marathons
If you really want to have the chance to run great marathons than I would only recommend you run around 2-3 per year. That way you can focus on a decent 12 week build up and have a much needed rest in between the races.
Train at a faster pace
Less marathons also allows you to train and race for shorter distances, such as a 10k. This will not only break up the long mileage needed for the marathon but allow the legs to run 'faster' than you would do in marathon training. This in turn will help your marathon pace – the more comfortable you can get at paces quicker than marathon pace, the easier marathon pace will feel.