Getting through airport security

What is it?
There are some simple things anyone can do to make dealing with the TSA less painful and assure your get to your gate on time.
Why do it?
You don't want to be that person doing a mad dash through the airport, hoping they'll hold your flight. First off, they won't. Second off, you'll end up on the plane needing to use the bathroom or starving because you had no time to deal with it before hand. Or you'll be that person in front of a Road Warrior slowing them down and making them angsty.
How did I learn it?
I started flying for work just a few weeks after 9/11. I saw first hand all the steps the TSA went through figuring this out, and that was a little painful. Currently I fly about every other week, so I have this pretty well down.
How do you learn it?
Honestly, follow these tips and you'll be in good shape!
1) Pack wisely - If you're planning to check a bag, put as much as you can into that. Specifically, put all your toiletries, multi-tools, pocket knives, tools, and non- essential electronics. The less you have to explain to an agent, the better. Check the TSA banned carry-on list and accept it as gospel.
2) Carry-on - When packing your carry-on, smaller is better. Space WILL be limited on the plane, but it's also easier to muscle a smaller bag through the scanner and tote it from gate to gate. If you're taking a laptop, don't strap it down yet, it will come out later. Also, leave enough room in your bag for the contents of your pockets. Finally, if you have toiletries in your carry-on, put them in an outside pocket.
3) Toiletries - are a pain. At this point, they really don't check often to make sure it's under 3.2 oz (that .2 comes in handy, BTW, on certain hair products!) but stay small to be safe. Big items DO get pulled. All liquids and gels go in your 1qt ziplock, but I put that ziplock in a mesh bag with my other non-liquids, like toothbrush, razor, deodorant, comb, etc.
4) Heading out - The TSA tells you to arrive 1.5-2 hours before your flight, which is likely overkill, but I stick to it. I'd rather be sitting in an airport for an extra hour than sad they wouldn't let me on. Honestly, at this point I have so many points and miles I get to skip most of the security line, but I still show up early. Parking, security lines, shuttle buses...any of these can be a hiccup. Finally, put on your easiest shoes to slip on and off, then out the door you go!
5) Checking in - I often do this at home before leaving, especially when flying Southwest. This is really great when you don't check bags as you can print your pass and walk straight to security. Drop 30 minutes from your arrival time if you're flying this way. Add 30 if you're flying with firearms. Have your confirmation ready and your license out.
6) Prepping for Security - before you get to the line to the gate, your real work begins. Put everything in your pockets into your carry-on (or jacket) EXCEPT your boarding pass and ID. I also often put my belt and watch in if I have the space.
7) ID check - hand the nice person checking IDs your boarding pass and license/passport. Don't fidget or fuss, but be polite and friendly. This can actually save you time, as they often have control over the one you head into, so if they take a liking to you they'll send you to a faster one. DO NOT say the words bomb, gun, terrorist, etc. They don't like those jokes. Also, do not downplay their job or share your opinions on the Theater of Security. 
8) Queuing up - pick what looks to be the fastest line. Avoid the one with a family with kids or old people in wheel chairs. Also, when possible avoid vacationers. Find the one populated with folks in business attire, or that already appear to be ready to go, even though there are 2 or 3 folks in front of them.
9) Bins - Once you get to the stack of bins,your real work starts. Take one if you have no laptop, 2 if you do. Throw your laptop in one, stack the other on top, then start loading up with your shoes, toiletries, watch, belt, ID, and boarding pass. I put the whole mesh bag in the bin and don't separate the ziplock out. Put them on the rollers, followed by your bags. If space is limited, stack your bags on top of each other. Do a final check for any metal on you (earings and wedding rings are fine, leave them on), then wait until your last bag/bin enters the X-Ray. Seriously, wait! I have seen folks go through and others jump ahead or the TSA pull it out when they don't know who it belongs to. Wait!
10) metal detector/body scanner - This is the biggest controversy in recent years. Most aiports now have the back scanners that caused all the hoopla. The TSA has gone through lengths to only show "hotspots" to their agents which then need a pat down. Anything, including paper, will show up as a hotspot. Multiple layers of fabric can as well. This is why we put everything in the tray. The metal detector is only picky about metal, but you may not always know which one you'll be going through. You can opt for a pat down if you prefer. And if you wear a kilt, you will get one more than likely. Ask me how I know! ;)
11) The other side - wait patiently for your bags. If they have to check one of them, DO NOT reach for it unless they tell you to. They will wait till your other bags come through to check it out. Be aware that tools of any type will normally get yanked, so check them before you get here. Also, multi-tools are a no-no, except for the new TSA approved Leatherman Micro, which you will have to explain each and every time. Trust me. Once you have your stuff, get out of the way to re-dress. Don't cause the rest of the line to wait for you!
What else can you tell me that may not be common knowledge?
Always double check your carry ons before you go! You don't want to lose something to the TSA due to your negligence. And it really does get easier with experience. Soon, like me, you'll be cursing the amateurs in your path!