If you are a daily (or near-daily) cannabis user, you've likely run into the "Smoker's Dilemma" before. Your regular usage consistently builds tolerance to the point that it takes a considerable amount of bud to feel the expected effects. This can continue until you are running through multiple grams per session just to feel anything, a pace that isn't sustainable unless you are either wealthy or have a large personal grow.
Resetting your body's tolerance is a matter of simply abstaining for long enough, but there are ways to do it that are much faster and more precise than simply going "cold turkey" until you can't take it anymore and hoping it works. These methods are especially helpful to those who need regular doses for the control of pain perception or appetite. Be aware that these only apply to vaping, pipe use or smoking, however. The physiological process that edibles are subject to is different and will increase tolerance considerably faster, even when only relatively small amounts are used.
Method 1: Fast Partial Resensitization
This method will not completely reboot your system to a virginal state, but it will drop the amount of cannabis you need to use by a very significant amount and only requires a break of a few days.
Start by totally abstaining for two full days. Early in the third day, take just one puff and wait for five minutes. If you feel any effect of the cannabis at all, cease use of it for the day. If you don't feel anything after five minutes, take one more puff and wait another five minutes. Continue this process until you feel even a small amount of effect. Once you hit that point, stop for the day.
Continue this process of puffing, waiting and ceasing as soon as you feel an effect for the next three days. In total there will be four days of this process, after which time you can start resuming normal use. When you resume your normal intake you should require no more than half the amount you were using previously to get the same effect.
This method was developed by Dr. Dustin Sulak, a researcher of the endocannabinoid system who publishes his work publicly through NORML.
Method 2: Complete Resensitization
Due to the continuing legal restraints placed on medical studies of cannabis, it's still difficult to say with precision exactly how long you need to wait or how much you need to reduce regular doses to fully "reboot" your tolerance levels.
What we do know about cannabis intake is that with large enough doses, the body will adjust to cope with this new source of stimuli by either creating more cannabis receptors, or by decreasing the function of the existing receptors. Ceasing all use for at least four weeks is a reliable way to both reduce the amount of added receptors and restore the normal function of the remaining baseline receptors that never go away. There will be individual differences, of course, but if you cease all use for a full month you should be good as new.
The estimation of one month is based on several existing medical studies of the function of CB1 receptors. What has yet to be determined is that if the different receptors for different types of cannabinoids will continue this process of degradation only if that cannabinoid is not present -- for example, if you were to continue use of a strain high in CBD but with virtually no THC, would your sensitivity to THC continue this reboot process even though cannabis was still present in the system?
While medical research still has a long way to go in getting the art of the tolerance break down to a science, these methods of partially abstaining for four days and fully abstaining for a month are backed up by what research we do have and also by individual anecdotal experience.