Vaccines don't cause autism.
There are two legal causes I know of where autism was linked with vaccines. In one case, the girl had mitochondrial disorder and was given too many shots at once. In general, doctors don't recommend getting too many shots at once, because it's a burden on the immune system, so if your immune system is compromised, you have to take it easy and spread out the shots.
As for things that MIGHT "cause" autism (or more precisely, some autism-like symptoms that may or may not really put you in the autism spectrum), I think we should reflect on all the other crap we put in our bodies. Pollution in the air and water, pesticides, the really shitty diet Americans eat, and so forth. A highschool in the southeastern US changed its lunch program to include primarly healthy foods: Behaviorial problems and absenteeism were reduced substantially. Eat better, and you'll think more clearly. This works on anyone, and helps alleviate some of the symtoms experienced by people with ASD.
Recently, autism was linked with some neocortical malformations. I'm not sure what is the cause of the malformations. But in some cases of mild autism, dietary changes anecodotally appear to help. Lowered immune system load and toxin load may be associated with some reduction in some autism symptoms. In my case, dietary changes have helped substantially with fatigue, brain fog, and OCD. I haven't narrowed down exactly which changes have helped the most, but I avoid wheat, soy, and dairy, and I take vitamin supplements only in their biologically active forms. My wife has Hashimoto's disease, so she got on the auto-immune SCD diet (similar to paleo), and following that to a degree has helped me too, and I also lost weight. Also, it's good to maintain a good array of intestinal flora, so eat your cultured vegetables, and drink kombucha and kefir. These things don't treat autism, per se; they just mazimize your baseline health, which can help with all sorts of disorders that might otherwise cause you more trouble.