Mr Weeds,
I'm no expert, far from it and have no special macro set up. However, I am the proud owner of a Jessops off camera flash cord (much cheaper than OEM variants) and usually use that when I use flash for macro stuff. It allows you to position the flash much better than is possible with a flash on the hot shoe.
If money was no object, then I'd go for a ring flash, that fits around the lens or I'd get a second flash unit (coupled with a few reflector cards) for a more even lighting effect.
Probably not the help you where hoping for, but the sum total of my knowledge
Edit ............. If you've been to my web site and looked at the 'Photo' bit, I can hoinestly say that the 3(?) samples of macro there where done using the 'suck it and see' method.