Once you've started collecting, make sure you don't go back for any you may have missed, once you've started its best not to turn back until the star has appeared, this will help to leave as many platforms untouched as possible for the trip back. Work your way from the beginning of the course all the way to the end, jumping in zig zag motions from platform to platform as to collect as many coins you can. Make sure that the 'last' area you collect, is where you have to long jump four times to get a massive amount of coins. The area where this is located is the very end of the stage, on the right hand side. That is why it should be last, and you most likely will have 100 coins by the time you have long jumped for them all. Really the best way is to make a pattern of collecting, sort of like a course for yourself. What I just explained was my pattern, and it works very well for me. Everytime I play that level I get it almost everytime. Anyways good luck. :)