Make sure you'll have access to the post race fluids and food you'll need immediately after finishing.
Although there are many commercial post exercise products to consume, healthy whole foods work just fine.
Be mindful of consuming too much fluid after the race. I assisted in a study on runners in the 2005 Manitoba Marathon and we found that some runners over consumed fluids after the race, which can cause hyponatremia; too much fluid intake dilutes sodium levels which in turn can cause the brain to swell, which could result in death (a nasty side effect).
About 500 to 750 ml of carb + electrolyte drink consumed within the first 10-30 minutes after finishing is enough.
You're looking to match your post race weight with your pre-race weight as a guide to how much fluid replacement you need. It's ok to take a few hours to make up any difference.
Trying to replace your fluids lost in race too quickly in large amounts (2 or more liters within 1-2 hous) is where the greatest risk of hyponatremia is.
Overhydrating is less common than under hydrating; being mindful both risks is important.
Another litre of fluids over the next three hours is a good idea especially after a hot marathon.
A quick mild stretch after the run can help prevent tightening up, but isn't 100% necessary.
It's best to head home, shower, and kick back on the couch as soon as possible.
It's best to avoid alcohol after the run as studies show booze after physical activity impairs recovery.
Studies show that the less fit you are entering the marathon the more damage to your body there is. Part of managing your post marathon recovery is proper preparation. Many people suffer unnecessarily after a marathon by pushing too far beyond their current abilities or from getting caught up in the attraction of the marathon challenge when they're not ready for it.
In general it takes around 3-4 weeks to recover physically and emotionally from a marathon.
Physically, blood markers of muscle damage return to normal within 3 to 7 days post marathon, and the leg muscles ability to contract normally again occurs between 4 to 14 days after the long run.
No running for the first 4-5 days is a good strategy for maximizing recovery.
See a registered massage therapist for trigger point work or even for a relaxation massage.. Your body deserves it!
Non-weight bearing exercise like swimming, cycling, or roller blading is a good idea for your first couple times returning to regular cardio.
There's no need for intensity yet, or going long. Don't worry about losing fitness from not getting back at it for a couple weeks.. You won't lose any fitness with a week or two off, and the recovery process will improve your fitness.
Between somewhere around end of the first and fourth week post marathon, very gradually increase the duration of runs and think about intensity 3-4 weeks post.
You won't need any more than 1-3 runs per week in the month following a marathon and many people do well with no running with 2-4 weeks after.
Watch your resting heart rate every day after the marathon and definitely avoid training if resting heart rate is still elevated.
There is variability between people for when it's best for them to start getting back to regular running. About half the population is more tolerant to more training, with the other half being less tolerant. These high and low volume responders need to be mindful of their individual needs and avoid feeling compelled to start running again just because somebody else already has.
Avoid peer pressure to push too soon.
Take the time you need get back to normal and you'll be back to enjoying running healthy again.