Growing and taking care of your mustache is a pretty simple task. All you really need is a pair of scissors, some mustache wax, and time. The first thing to learn is about the nature of mustache's; in that they hit terminal length at a pretty short length. For instance, my mustache will only grow to about the bottom of my chin. For many other guys, it's even shorter. That's ok!
I personally never trim the middle section and let that be completely natural. I will however trim the edges of my beard. The spot you trim your mustache really depends on your own natural movement of the stache. For me, I've found that cutting it about 1.5" from the edge of my lips is the best spot.
If you are going for a corporate beard, then it's going to be acceptable to trim your upper lip. Generally speaking, the bigger beard deserves a bigger mustache.
To use mustache wax, scrape wax off, warm it up between your fingers, and work into the mustache. You can use a hair dryer to give it a little more even distribution; but I've found it works great without using the dryer as well. Using Beardbrand mustache wax will give you a natural look and hold that keeps everything tidy.
It won't give you the handlebar mustache, which you'll need a higher hold mustache wax for.