Sniff tip:

Throughout the game, sniff everywhere!!! You need to 
collect melons and most are hidden to the eye, but not
to Yoshi's nose. If you get 30 melons in each level, 
you get a perfect score, but only in the melons section. 
Poochy will help you find an area to sniff in. Oh, and
you can only eat the certain color fruit or shy-guys as
your Yoshi (Ex. Green Yoshi can only eat green 
fruit--green melons--and green shy-guys or else he may 
lose life) NOTE: If yellow Yoshi sees a blue shy-guy, 
pound the ground to turn him yellow. Of course, this 
works with every other color yoshi EXCEPT black and 
white yoshi, which will and can eat any color 
fruit/shy-guy. They are RARE!

By Nick