You'll get the most from jumps coming off ramps or mountain ridges, when you see coins and gears lined up in the air to collect.
For backflips, use these maneuvers when you're really high in the air. Otherwise, you'll hit the ground headfirst.
You can boost two ways:
1. The first involves collecting three or more coins in a row, which are usually strewn together over objects and ramps.
2. The second is by successfully completing backflips. Chain the two together, and you'll create a non-stop boost for several seconds.
Save coins for animal sidekicks, before investing in a new bicycle.