A little maintenance can go a long way toward an enjoyable time on the slopes. If your edges are dull they won't bite in when you make turns. If your skis are dry (no wax) they won't slide as easily, which means you'll go slower and have more trouble on level ground.
So here's how I've come up with to sharpen and wax in a cheap, but fairly professional way.
Cheap Clothes Iron
Piece of Acrylic (scraper)
Step 1: Evaluate and Tie Brakes
It's pretty much impossible to wax too often, so unless you've just done it and haven't been skiing you might as well wax. As for sharpness, the rule of thumb is that if you drag the backside of your thumbnail across (perpendicular) to the edge it should shave a bit off your nail if it's sharp enough. If not, sharpen.
Before you get started you'll want to tie the brakes up on both skis, just to get them out of the way. To do this just run a string or wire from one side, over the heelpiece and around the other side. This gives you full access to the base of your skis.
Step 2: Level Base
The main body of the ski that contacts the snow is called the base, the edges are the metal strip along the edge (obviously). You want to start off with the base and the edges flat and level. My base was worn a hair below the edges so I used a file held flat to take the edges down. If your base is higher you might be better off with a sanding block than a file.
I found that the best way to support the ski was to wedge one end against the floor/wall corner and support the near side between my knees (while sitting), work half the ski, then flip it around.
Step 3: Make Cardboard Jigs
So I was looking around the internet and found this which is great but a little pricy. So I figured I could make something similar from cardboard (reinforced with tape).
You want a .5 to 1 degree angle, so go to this site and calculate that. Use "calculator 3" and put the thickness of your material as "side a", and the angle you want as "angle A". "Side b" is the distance from ski edge to "elevation bar", in other words the length of the cutout in the template. This distance should be measured at 90° to the ski edge, even though you're going to cut the template out at 45°. The template is angled 45° so that the file will bite, files don't work when moving sideways.
I made two templates, one for a file, one for a diamond hone. I actually didn't need to make two, the larger one would work for both.
Step 4: Sharpen and Hone
I found this was the best way to hold things, thumb providing down pressure, the knuckle of my pointer finger is against the bent-down section of cardboard holding everything over where it needs to be.
If your skis are in decent shape you can skip the file and go straight to a hone. Stick with your coarsest grit (file) until the entire edge is fresh, but not so far that you start filing the base. Color a bit of the edge with a sharpie if you want to see how well your angle matches the existing, or to check progress. Then progress through finer hones if you want. I did: file -> 150 -> 300 -> 450
Step 5: Waxing
You can get different waxes to be good at different slope temperatures, or all-temp wax which is okay at all temps. The chunk I have is half for above freezing and half for below, I'm never sure what the weather's going to be like, so I mix them.
Clean the surface of the ski well before you start waxing, this is done with a scrub brush or brass brush, you want some texture.
Wax someplace you don't care about getting wax on things.
The wax is going to end up in the steam holes of the iron, which means you're not going to want to use it for clothes anymore, so get yourself a cheap one (despite the tag I got this one for under $2). Set the iron to a low/medium heat, where the wax melts quickly, but doesn't steam. Drip wax off the tip of the iron onto the ski. Then iron it in, you want to move slow enough that the wax penetrates, but not so slow that the heat hurts the ski.
Step 6: Final Scrape and Clean
Take your piece of acrylic and scrape the excess wax off. Angle the acrylic slightly in the direction you're moving. The idea is that you only want to leave the wax that penetrated into the ski. Also be sure to scrape the edges.
If you scrape one ski before waxing the other you can use the scrapings to wax the second.
After that just brush them off with a medium bristled brush (almost scrub-brush stiffness). This cleans off the last shavings from scraping and puts a bit of texture into the remaining wax, which helps the ski glide better.