Sorichuudo
Smash Ace
I actually use pellets more for spacing and to stop opponents from going aggro on me, but you might start with this video for a few tips on playing MM :Is there a good guide on the use of pellets? I sometime struggle to capitalize after getting some of them to hit.
https://www.youtube.com/watch?v=8oxbjcKBXX4
There is also a few threads for useful info on MM in general:
http://smashboards.com/threads/how-to-win-with-mega-man.376584/
http://smashboards.com/threads/wood-mans-treehouse-a-leaf-shield-guide.374719/page-4#post-18237077
http://smashboards.com/threads/lets-blow-stuff-up-a-guide-to-crash-bomb.377296/#post-18274718
http://smashboards.com/threads/mega-guide-for-mega-men.373533/
Check them out, opana's mega guide in particular has some useful info on pellets, tho i haven't read it after the 1.04 patch so i don't know the changes there, it still is worth reading.