In colder weather, I suggest wearing a long sleeved black shirt with t-shirt over top, usually in a bright colour like hot pink, red, or a light grey. If you are a guy, either wear a long sleeved shirt, or a t-shirt with an unzipped sweater/jacket over top. If you have scars on your legs, merely wear pants.
In hot weather, it's a lot harder to cover-up and not raise suspicions. On forearms and wrists, foundation (a liquid of your skin tone; make up) can cover most/all of it. Wear lots of bracelets (bright, colourful beads), wrap a bandana around your wrist and safety-pin it so it won't fall off, wear a heavy watch, or even wear gloves (I cut the fingers off mine). If you are in a pinch and are a little tight on cash, tights/black nylons cut in a forearm's length works really well (cut a hole for the thumb so it won't fall off).
If you are a girl, you can wear a light coloured tank top (for example, a light blue), with a white, long sleeved, unbuttoned shirt over top. If anybody asks, you can tell them you burnt your shoulders really badly and they're too sensitive for the sun. Or, you could just say that you don't want to burn in the first place.
For scars on leg in the summer time, I wear long flowing skirts, knee-length shorts, capris, short skirts with tights, and I have a pair of cut-off jeans (really short) and I wear tights underneath.
