remember scoring is as important as speed for them medals.
Gotta disagree with this. I unlocked every character the first day the game came out, and I think speed is by far the most important aspect of scoring. The only score objects I ever go for are balloons, and even then they're not worth losing my momentum over.
scoring is just as important as speed! I ended a couple of times just a point or two under the gold medal! :D
Anyway, most of the ballons are placed in ways that won't take your momentum away, and there are some baddies that can easily add to your score whitout losing momentum... so to quote valter, "requires some rather creative running". I just run and run and run and run over a course over and over until I get it right!
edit beacuse I'm daft and I forget things the minute I thinked of them:
Also, it's critical not to make any errors, as you might know the substract points, and in some cases (such as the fire walls) can easily lower your score about 50 points, you lose all the momentum. This one it's a fucking precise game.