I have heard many times that you shouldn't have mining and herbalism on the same char, but after WotLK came out I decided to drop alchemy on my alt, and took up mining instead. I have to say that I'm rather happy with the combination. I started out by just having one tracker enabled at a time, shifting it once in a while, and keeping an eye out for the other type of node, but since I got to lvl 77 and epic flyer, I've been using a really neat macro:
#showtooltip
/castsequence !Find Herbs, !Find Minerals
It swaps the two trackers, and I've got it keyed to 'T' so I can easily get to it when I fly around, and by swapping very often I get all the nodes that I pass. Sure, it's more of a bother than only having one tracker up at a time, but the huge amount of mats that you gain more than make up for it IMO.
Has anyone else tried this?