In order to minimize crosstalk between inductors, as a general principle, try to orient them at 90 degree angles to one another. For example if the axis (hole in the middle or core of metal) of inductor #1 is pointed north-south, orient inductor #2 east-west and inductor #3 up-down. If you have 4 or more inductors, try to have two right-angled ones physically more or less in between each pair that share an orientation. Keeping the inductors as far apart as feasible is also a good idea, as the induced field strength falls off with the square of distance.
Inductor cross-talk (the field of one inductor actually inducing a low-level replica audio signal in another, no physical connection necessary) is real, but may or may not be audibly significant. Still as long as you have to mount the inductors anyway, might as well stack as much of the deck in your favor as possible.
EDIT: Poseidon's diagram below is better than my description. Use that.
Secure all crossover elements tightly to the board so they don't vibrate. Physically double-check all solder joints and connections; a poor connection can still pass signal, but become intermittent over time. This is much easier to do before you install the crossover.