I agree with infzy. Sonic is really one of those characters you need to practice with a lot to get used to. Whenever I first picked him up, it took so much time to get used to how freaking speedy he is. Be very expectant to run/spin dash/charge off the stage, Spin Dash/Charge into the side of a stage, or DAir off the side. Some of the changes that were made to him from brawl that might be useful to you, His FSmash was buffed, his BAir was buffed, DAir is now a meteor smash but deals less damage, his Up-Throw and FAir deal half the damage they did in brawl, homing attack has less start up lag/more knockback/ less damage. Take this information as you will, but enjoy your time playing as sonic.
