I recently completed my first skull plate mount of my buck antelope from the 2010 season. I used a kit from Van Dykes, and I thought I would pass along the tips my dad shared with me, as well as one or two I figured out on my own. I have only completed the one antelope kit, but these tips should work for kits for other species as well.
1. Leave as much depth to the skull as possible when you remove the antlers/horns from the skull of the animal. This gives you more skull to work with as you try to make a nice, flat cut at your desired angle for displaying your antlers/horns. I think skull plate mounts look better if you can tip the horns back, rather than having antlers/horns come out perpendicular to the plaque.
2. Use wood shims and glue to stabilize and adjust the angle that the antlers/horns come off the plaque.
3. Use a hot air gun to heat the plastic cap. It makes the plastic more pliable and easier to trim in order to make the antlers/horns fit better.
4. Use needle-nose pliers to hold the tacks as your start hammering them into the plastic cap.
5. Use a tack hammer. You can use a normal hammer, but the smaller hammer seems to result in fewer bent tacks.
6. Start the tacks into the plastic cap before sliding the cap over the antlers/horns. This makes it easier to get the tacks positioned where you want and get them started.
7. Use a transparent glue to hold the cord around the base of the antlers/horns. Use the cord if, like me, you need to conceal some of your mistakes as you tried to fit the cap to the antlers/horns.
Specifically for the antelope kit, I found that popsicle sticks work well to mix and apply the horn glue while a small Styrofoam cup worked well to mix the glue in.
The directions that came with the Van Dyke kit were adequate, but they definitely leave room for you to try to improve on the process. I am entirely a beginner when it comes to completing my own skull plate mounts, but these tips that my dad shared with me definitely saved me some frustration. I am not incredibly gifted when it comes to working with my hands, so if I can do it, anybody can. I like skull plate mounts as I think they offer an economical way to create a nice looking display of your most recent trophy. The satisfaction that you get from doing it yourself is simply icing on the cake.