In Badlands, if you complete a race with 2 or fewer wrenches, the game has a "buy-in" feature that lets you buy 9 more wrenches for 1 credit. Because the games are always set to Free Play, you always have infinite credits, so essentially it amounts to free wrenches! There is no limit to how many times you can do this during the game, but it can only be done when you have 2 or fewer wrenches before entering the shop and only once per race.
A couple of levels have hard-to-reach tunnels near the beginning, preceded by a boost pad. If you can hit the boost and reach these upper tunnels, you will warp ahead several levels and earn 20,000 points.
When the pre-race countdown begins, do not begin accelerating until the "1" begins to disappear. When it does, begin accelerating and as the race starts, if done properly, your boat will reach top speed much faster than normal. You will hear a voice shout "Super Start!" a few seconds later if done properly.