When in doubt, try a cheap experiment.
Make a list of various forms of recreation, then do one of them for some amount of time whenever you feel the need to take a break. Afterwards, note how well-rested you feel and how long you performed the activity. It shouldn't take many repetitions before you start to notice trends you can make use of.
Although to be honest, the only conclusive thing I've learned from trying that is that there's a large gap between "feeling rested" and "feeling ready to get back to work on something productive".
Anyone offering a single, specific "best" way to rest is likely to be committing the typical mind fallacy. For example, there are people - extroverts - who "unwind" after a work week by going out to clubs. As an introvert, I have a knee-jerk inclination to suspect such people of genuine insanity, because such an activity would have no relaxing or energy-restoring effect for me. Of course, they are no more insane than I am, just psychologically different, but those differences can have a big impact.
As wgd suggests, you can experiment to figure out what is most relaxing for you. Another possibility: if you could provide more details about your own psychology, people who identify with those details could offer their preferred methods. Without more information, I think we will just be other-optimizing.
I have no idea. I found that really good isolating headphones, listening to a 15-minute electro track, and just laying on the floor breathing deeply has been more restful than the average 15 minutes recreation.
Also side projects learning something (recently code) seem to vitalise me.
It might just be because I have ASMR, but watching YouTube videos of medical examiners describing examination procedures is extremely restful / re-energising for me.
For knowing when and how long to take a break, the Pomodoro technique is worth a try. You basically alternate between 25 minute work sessions and 5 minute micro-breaks. The breaks are too short to actually do anything in, just step away from what you're doing (probably on a computer terminal), walk about a bit and space out for a couple of minutes. Start with the default technique, then adjust the intervals to see if something works better.
A lot of my idle time goes to browsing the web, but I do worry occasionally that there's something to Alicorn's experiential pica idea, and browsing vapid stuff is just a self-reinforcing cycle of uselessness.
It might be also useful to separate breaks as switching gears and breaks as rest. Running and concentration-intensive meditation can both require exertion, but they're also quite free of the sort of demanding decision-making you need to do when working, and could be considered rest along that dimension. The exercise aspect will also hopefully boost your physical and mental stamina. I don't know what's the good amount to spend running or meditating though, but at least both activities have reasonably natural session lengths (time to run some familiar route, around 30 minutes meditating), so it's simple to do something like 1 session a day or a few sessions a week, and end up with probably not that bad parameters. (On the other hand, I have a hard time figuring out what kind of bodyweight exercise routine is long enough, so I end up doing nothing at all.)
Instead of resting perhaps think of how you can generally increase your energy level throughout the day. I've noticed much attention paid on this site to drugs like Modafinil. However I've also noticed most people don't appreciate how much of a difference eating right and getting enough sleep can truly make. I know this is blindingly simple but usually the most powerful tools usually are.
Fruits, vegetables, fish, whole grains, etc.
So, not paleo then? I ignore paleo myself, but it does seem to get a lot of traction in rationalist circles; whether because it is actually beneficial or just a rationalist fad I don't know.
You know I've actually been researching paleo in the past couple of days and I've been really curious about it. I've noticed the interest rationalists have in it too. Honestly it doesn't seem that bad to me. I'm just curious if it has all the effects it claims.
Men's Health seems to have some good stuff on nutrition. I like especially how the magazine has lots of healthy recipes, but there's lots of stuff at their website too.
Men's Health would be about the last place I would suggest looking for advice about nutrition. Magazines almost never cite their sources, so you have no idea what quality of information they are writing from. I believe that the majority of their advice comes from epidemiological studies, which are very low quality sources of information.
I like to do something physical to take a break from intellectual pursuits- sailing, or hiking usually.
It seems like physical tiredness and mental tiredness are mostly non-overlapping: I can go hike all day and then come back and work at a desk without fatigue, or vice versa.
I recommend timed breaks (so you don't have to worry when your break should be over), walks, and relaxation hypnosis.
Ultimately you want to learn what kind of fatigue you're suffering from and figure out what kind of break is appropriate for it.
I recommend timed breaks (so you don't have to worry when your break should be over)
This is diametrically opposed to how I react to being timed.
I'd suggest doing something you enjoy and doing it consciously as a reward for the work you did. Doing boring things might deplete your willpower and is not relaxing.
I've always been fascinated by people who are unendingly engaged in creative and/or productive activity. I've known a couple of individuals who do not appear to rest, ever, who hated sleeping. I've long wondered if these rare people were simply resting in some secret super-effective way for brief spurts, or if it they were innately superpowered. You could say one of my obsessions is to try to understand the Infinite Energy Hack so that I can implement it, if it is learnable.
It might just be superpowers: http://online.wsj.com/article/SB10001424052748703712504576242701752957910.html
My personal experience is that these people are unhappy (self reported and observation). But that's kind of a stereotype and I think there are probably plenty of workaholics whom are quite happy.
This is interesting; my model predicts the exact opposite.
My model is that mental work does not make you tired, it makes you frustrated. There is a difference, because "tired" is related to how difficult the work is, while "frustrated" is more context-dependent -- a simple but time-consuming meaningless task can be very frustrating, while solving a difficult but interesting problem, if you believe that you can do it, is not frustrating. Even expecting a work with unpleasant connotations can make you feel tired.
When I have a lot of free time and something very interesting to do, I can do it for hours and feel happy, at the evening I go to bed thinking about the task, and the next morning I jump out of the bed looking forward to the task. On the other hand, when the task is unpleasant, I try to avoid it by whatever means possible, and in the morning I can't get out of the bed. At least for myself, when I have no problem working, I am happy; when I am avoiding work, I am unhappy.
Of course a larger context can change this. A person happy at work could be using the work as a way to escape from real-world problems. The problem is not with being productive at work per se, but with failing in the larger context.
At least some of the people who get a lot done are bipolar-- I believe this because some of the people whose livejournals I read eventually mention the diagnosis.
So, it's well-known (or, at least, oft-thought) that you can't just work 16 hours a day; if you want to get stuff done, you need to rest from time to time. You have to take breaks.
Today, just now, I realized that I don't really know what the best way to rest is. If I want to rest, should I do something that's fun and interesting, like reading a fantasy novel? Should I do something that's boring, like building roads in Minecraft, so that work will seem comparatively interesting when I get back? (And besides, reading a fantasy novel is a bit of a challenge, at least for me, whereas building roads in Minecraft is trivial.) Physical activity probably helps, but how much? Do relaxing activities, like taking a warm shower, help more than just sitting there? How can I tell when it's time to take a break? How can I tell when it's time to get back to work?
(Suggestions for tags would be appreciated.)