Spider veins, just like the larger varicose vein counterparts, are a result of increased pressure and vein valve malfunction, only on a much smaller scale than varicose veins.
The first step is identifying bad habits that can lead to increased venous pressure. If your job involves long periods of sitting or standing, find time to walk around every hour. Avoid crossing your legs when sitting. High heels do not allow the calf muscle to function well, so avoid wearing them to work. When possible, elevate your legs; at night, leg elevation will help with mild leg swelling. Proper compression stockings are the the best form of medical management. The external compression not only helps with leg pain and swelling, but also prevents progressive vein dilation. Walking every day or some other form of exercise is the best way to prevent varicose veins from worsening.