A temporary power-up will become enabled when your coin meter has completely filled up and you then double-tap anywhere on the screen. Always use these power-ups as soon as they become available.
At the end of a run always make sure you grab the roadside keys as these give you the opportunity of picking a music box at random which gives you the possibility depending on which one you pick of getting a good points bonus or coin boost.
Following the correct directions when you reach a crossroad sometimes gives you the opportunity to switch to a different environment. When this happens all you have to do is keep running until the new environment meter has become completely filled up.