SHL -> SHL -> SHL BACKWARDS FOR MLG PRO MIXUPS -> SHL -> Empty SH -> WD Back -> either Nair, Fsmash, shine, shine grab, Dair = a typical approach on a Marth for me might look. Since Swordguy has so many opportunities to murder Laserbird, you need to be smarterer than the dude with the big letter opener and out shoot him, much like you may have seen PC outgun Ken this last salty suite. Mixups to bait long swings or ill - advised grabs are what space animals THRIVE on in the Marth matchup, so get in there so you can get back out. Give him the ol' shake n' bake. Juke the piss out of him so he falls ass over teakettle.
Nairing at the bottom of people's shields is really useful when you've pressured Marth into the corner, near a ledge. This will push him off and make him grab ledge, leaving you free to calmly walk up and downsmash on ledge or SHL to your heart's content so that you can Dair him off ledge. In other cases, I'd advise either spacing your Nair so that you pass through his shield, or spacing it so that you land just behind so you can trick him into thinking he can grab you and then Shining him so hard he turns into Jack Nicholson.
