Finding the right preventive medication is usually a looong process of trial and error. I've been on 5 in the last three years, and am about to try Botox.
But in the meantime, there is a lot you can do to improve your quality of life.
First, are you keeping a migraine diary? That is very important to help you identify your triggers. Trigger managment is half the battle. Keeping a list of what you're eating, or what you did that day, or what the weather is like can give you a better idea of what is triggering your attacks. That can help you avoid them, or at least know when they are coming.
What about lifestyle changes? Three things I always recommend are 1) sleep hygeine 2) stay hydrated 3) cut out as much processed food as possible. For the first, a good nights sleep is really important, and lack of sleep is a common trigger. Also, being tired will often make us more susceptible to other triggers. Second, staying hydrated is important, because dehydration is another stackable trigger. As for number three, even if you don't have food triggers (I know I don't) all the gunk and garbage in processed foods really isn't great for our oh so delicate systems.
Also, you can try yoga, tai chi, massage therapy, acupuncture, aromatherapy. They may not be preventives, but like chicken soup, they couldn't hurt