You actually have to solve it a little like a rubik's domino. First you have to solve the middle two layers with domino algorithms and then the top and bottom layers the same way.
Here's a video on youtube that shows how to solve a domino and the guy shows several easy algorithms for the domino
Interesting. I'm ordering a 3x3x4 tomorrow so I'll have a look at it myself next week. Maybe you should solve the outer layers first? I'm not sure I need to try it out myself. Hopefully someone else can explain.