Since I've been wargaming for 40 years, I'm not going to try to cover all the things I've done in all that time. I'm just going to jump right in with projects that are ongoing now.
So let's begin with the basics: bases. I have a variety of sizes I use depending on the scale and the timeframe; ie ACW, Vietnam, etc., and what sort of unit I'm basing; infantry, an armored vehicle, etc. I prefer to use metal bases, as it allows me to put magnetic sheets in the bottom of my storage boxes and prevents damage when moving things around. Most of my bases, I get from Wargame Accessories
Here's a 40mm x 30mm base that I use for my 3mm modern minis. After I straighten it out so that it sits level (they come a bit bent up), I'm ready to make something with it. If I add a small hillock or other terrain feature, I seal it with Flexpaste, as some paints will dissolve styrofoam.
Terrain feature or not, the base gets a coat of light grey primer. Paints and texture pastes don't tend to stick too well to bare metal
Then I give it a coating of Vallejo White Pumice Paste (for Western Desert bases, I use PVA glue and fine sand instead)
Once that's good and dry, I give it two coats of a soil-colored paint. I like Stone Mountain Miniatures Mud paint.
Then, because of the small scale, I use quite a fine summer grass flock by Woodland Scenics and generally top that off with a scattering of fine burnt grass flock. The whole thing is then liberally bathed in Scenic Cement
I usually leave a bare patch or two, just to break up the "pool table look". Now it's time to use some superglue gel to attach the minis
In this case, two 1/600 West German M107 self-propelled howitzers from Picoarmor. I then add a bush or two, glued down with Scenic Glue. I give the whole thing time to dry and finish off with a coat of Testors Dullcote. Viola!! One based mini!!