600mg is recommended. But yes, it probably varies from the size of the individual. I just say pop it back, gradually up the dose and see what works for you.
Signs that it's working I would imagine... less subcutaneous water retention, possibly increased endurance (due to more glycogen), and overall just a better "tone", for lack of a better word. I've never played around with it myself. That would be my guess however.
I should really look into that.
Do you take ALA straight with a shake, or do you take it in a mixed supp like with Glycemet? You may want to watch Chromium intake with Glycemet if you do.