Best of luck!
Your first all grain batch will also be a test of your mashing setup. This means you're working with unfamiliar equipment in addition to unfamiliar procedures. Lots of fun, but also lots of new ways to screw up.
Amylase enzymes denature fairly quickly; you have about 5 minutes to get your mash temperature down to where you want it.
Given the high degree of modification of most modern malt, starch conversion can happen fast - within about 30 minutes.
Conversely, most brewers run off their wort too quickly - for maximum extract efficiency, you want a slow trickle of wort. This also helps combat hot-side aeration.
(These facts from a presentation from a rep from Briess malt at the 2008 NHC.)
Practically this means:
Really sweat your strike temperature. Warm your mash tun with hot water before you add your grist, so you don't get too much of a temperature drop. Have a half gallon of hot (ca. 170 degrees F) water and a gallon of cool water (room temp.) on hand in addition to your regular liquor. Stir your mash well to get even temperature distribution and break up clumps of dry grain. Take a couple of quick measurements using a probe thermometer, sampling in different locations and at different depths to get a sense of how the water is flowing through your mash tun. Working quickly, mix your mash until you get an even temperature. Judiciously adjust your mash temperature using your hot or cold water until you're within a couple of degrees of where you want to be. After that, you're good. Messing with it won't help it. Leave it alone. Do something else.
If you must shave time from your brew day, take it from your mash. You can get away with as little as 30 minutes is pH, mash thickness, etc. is right and you're going for a dextrinous wort. Good reference here: http://www.howtobrew.com/section3/chapter14-6.html
For wort runoff, once you're sure that your system is working right set the valve on your mash tun so you're just getting a trickle of wort. If you're recirculating or fly sparging, adjust the flow so liquid is coming into the mash tun at about the same rate it's going out and the mash is covered with liquid. The idea is that you want the mash to "float" slightly so it doesn't get compacted (the dreaded "stuck mash").
Other stuff I've learned the hard way:
As you collect your runoff, also look for bits of grain husk and other crud in your wort. If you see that sort of stuff, carefully pour your runoff back into the mash tun until the runoff is fairly clear. Grain husks in your wort = astringency in your beer.
Don't be tempted to add more sparge water to get that last little bit of wort. That's another way to get astringency. Better to get a smaller amount of higher gravity wort. If you want to make up the volume, just cheat and add water and malt extract. After all, it's your first all grain batch! Who expects perfection the first time?
In some cases, crud can clog the outflow valve of the mash tun. Something like a pipe cleaner, bent coat wire hanger or chopstick is useful for clearing such clogs. You might have a clog if outflow suddenly slows severely, even if it doesn't stop. You can also tell if there is a clog if the amount of liquid flowing into the mash tun starts to rise.
If you do get a stuck mash, shut off the outflow, let some more sparge water or recirculated wort into the mash tun and gently stir the mash. Once the liquor covers the mash, you can carefully restart the outflow valve. The ideas is that you want to "refloat" the wort without creating "channels" through it. If worse comes to worse, though, just accept that you'll get crummy efficiency from the mash and get the runoff any way you can.
Eventually, you'll know your system well enough that you can nail your mash temperature without needing to mess around with hot and cold water, you'll figure out flow rates, and whatnot, so you will be able to pretty much ignore the mash tun, hot liquor tank and grant while they do their thing. Until then, sweat the details in the first few minutes of mashing and during runoff.