Well, veins coming closer to the skin aren't actually varicose veins - varicose ones are where the valves start to fail and blood pools around them. Mostly happens in the lower leg, and you get visible bumps, rather than just the veins appearing near the surface. I wouldn't worry about it unless they do start to look lumpy or cause you pain. I'm not sure about preventative steps etc - a quick google search should give you some information though.