It seems to vary from member to member.
As far as diet, I find I do best when eating a vegetarian diet that's mostly fresh fruits and vegetables (at least 80%). I also find caffeine helpful, but have Chiari Malformation and think it helps those migraines or low pressure headaches from spinal tap, overdraining, etc. I always suggest an elimination diet to figure out if you have any triggers.
I have found some symptom relief from Bach Flower Essences and just starting cell/tissue salts, but I'm pretty sensitive in general so the energy-based treatments work best for me.
I also find massage, reiki, and acupuncture helpful. It's usually short term, but my specialists have said it's beneficial even if you just get relief during the treatment. They all also agree that cranial sacral therapy is a bad idea, but I think that's because I have a shunt which gives me an open system. Other members have noted benefit with it. I would look through the Alternative & Holistic Therapy posts in the Living with IIH section (http://www.ihaveiih.com/f13-alternative-therapy) for more specific information.
I would say all of it helps with my symptoms, but the downside is cost because insurance doesn't cover any of it.