Generally, it depends on one thing: whether or not the opponent is in the air. If he is in the air, SHL -> Fsmash, or, for floaties, dtilt if he's close enough is fun. However, if the opponent is on the ground, shielding or not shielding, I mix up a few things such as SHL -> Dair or Nair through him or play the safer route and SHL-> Ftilt to try and keep spacing while possibly hitting your opponent. Mainly, though, I like to SHL -> Dash attack *Through* the shield, and Utilt once behind, assuming the dash attack didn't hit my opponent. From here, you can sh dair into a shine combo or utilt combo depending on percentages.
That's just my two cents though ^_^ I hope others can throw out some good ideas.