You can find blue coins by replaying levels. Blue coins will appear where trophies previously were found. Blue coins are worth 100 coins each.
Dynamite wick
Before starting a level, you will be given a chance to set to length of your dynamite wick is. The longer the wick, the more time are allotted, but the less stars that can be earned. The longest wick can only result in a single star, the medium wick two stars, and the longest wick three stars.
Helmets
Instead of spending coins on costumes, which are only cosmetic, save them for helmets. They convey passive bonuses that are useful. Purchase the brick helmet first, which allows Doo Doo to break through some walls, which often reveal items and secret paths.
Speed boosts
You are given three speed boosts at the start of each level. You can only have a maximum of six boosts saved. If playing with the shortest wick, use them as needed but always save one for tight situations.
Walls
Breakable walls are marked with a yellow diamond sign with red symbols on it. Use the brick helmet to break through them.