When my friends and I play 3-way matches, we do it one of two ways: 2 v 1 or a triangle board. The 2 v 1 just follows standard match setup, but the triangle board is a bit different.
We decide on a side length for all three sides, usually 4 feet, but it can change depending on game size. To determine who goes first, we all three roll dice. Highest gets to chose first, second, or third, and then the next highest chooses from the remaining two spot, and the lowest is stuck. Then, The person who is going first chooses a table corner, and he/she may deploy their models up to 12" from that corner. Second person deploys, then third. Objectives are easily modified to be used with three people, and kill points needs no modification.
It doesn't work quite as well as a regular match, but it does add an interesting twist to your games. Good luck with your match, and I hope this helped! :beer:
EDIT: Just read Wicky's post. That's exactly what my friends and I do for our 2 v 1 games.