I'm not sure how much the order matters, since even on a 3-antenna router or desktop wireless card all the antennas are identical and you just screw them in.
For what it's worth this is the system I stick to based on experience with differing laptops and mini PCI-e cards:
1 / TR1 / White triangle / Main
2 / TR2 / Black triangle / Aux
3 / R0 / Grey triangle
<insert large, flashing, epileptic-fit-inducing signature (based on the latest internet-meme) here>