Go on youtube and search for Linkology and The Hylian Nightmare... Linkology is done by Germ, probably the best link player in the world, or at least out of the ones i've seen.
Learn how to drop bombs instead of throwing them... also, NEVER pull bombs out on the ground... leaves you open. If you pull them out in the air, Link pulls them faster. Also, when your boomerang comes back to you it leaves you open. Either jump in the air when grabbing your boomerang or pull a bomb out to cut out the tiem it would leave you open. Or better yet, jump and pull out a bomb.
Other than that, work on your swordplay. Learn how to fast fall and platform cancel and you'll be solid. My favorite move is to short jump, fast fall into Link's D-Air move (sword plant), and then platform cancel and go into his smash moves. Lots of fun. :D