Going to second the l-tyrosine suggestion. It won't completely wipe out the comedown, but it smooths it out a lot, really takes the edge off it and allows you to put it out of mind and more or less go around your normal business.
Meth, I find the high varies a lot depending on how you administer it. Eating it will give a nice body buzz, but the mental rush will be a lot weaker, whereas smoking gives a much weaker body high, but a really euphoric mental rush. Snorting falls somewhere in between, you'll get the charge of energy, but you'll also get a nice headrush going. This is on top of the usual disrepencies you'd expect between methods of ingestion to do with potency/duration/speed it kicks in, etc.
Snorting is painful, but not 'omg ahhh!' rolling on the ground time pain. Just 30 seconds or so of 'ouch!' while it absorbs.
Do yourself a favour and avoid staying awake for insanely long periods of time, it really, really, REALLY, exarberates the crash afterwards. And if you do, try and take a break from constantly redosing somewhere in between. Expect to be unable to sleep for a minimum of 12 hours after your last redose, unless you have some valium or whatever to bring you down.
Be careful with your dose. It's very easy to take too much, especially if you're getting good crystal and you're not used to such a strong substance. Start out with maybe 30 - 50mg, and take it slowly from there. Too high a dose will just throw you into a heart racing, panicky, sweaty, twitchy, paranoid, angsty mess. I threw myself into that zone more than once before I got used to the drug and it completely killed my night on each occasion.
Personally, I'd say just stay away from it all together, the drug doesn't have much to offer anyone. It's fun yes, but the level of addictiveness/the shitty comedown/the longterm effects on your life are really out of line with the high. The high is fun, but it's a very hollow, empty, more-ish experience. It's not a satisfying 'omg this is amazing' high like MDMA, you'll feel good, but it always promises more than it delivers, and the longer you chase that high the worse you'll feel when you crash out at the end of it, and in the end you'll come out of the experience just feeling like shit, wishing you'd never done it, with nothing gained. But I guess it's always easier to say these things in retrospect.