To earn an easy nitro boost, do not try to plow through lots of big heavy objects on the side of the road. This only slows you down and you might get stuck in it. Instead, look for cones lining the track and hit those small cardboard boxes. Also signs are good to run through. These objects do not slow you down, and will earn nitro. Also, if you are going to slam into junk on a turn, try and slide sideways into it. You more or less will slide or bounce of it, losing less speed and you will not get stuck. This also works well with roadside fences, where you can just rub up on them and knock them down sideways instead of ramming through them directly.

At the first race from the left list, hit the scaffolds under the bridge to get all the nitrous you can. Be careful; there is a ladder at the right scaffold. If you hit it, you will slow down a lot.