How do I know if I hit with the tip of the sword?

Marth's biggest trait is that the tip of his sword deals the most damage. Is there a way to know if I am hitting with it?

Solution 1:

The only indication is that trail effect of attacks is brighter at the tip of Marth's sword, comparision between Brawl (top) and SSB4 (Bottom) below:

Based on that, you can get a better idea of where your attacks connect with the opponent. A general rule of thumb is to always play as far away as possible. A nice way to test this is actually in melee, where Roy was strongest when you connected with the broad of his sword, and Marth was with the tip. It actually led to some very different playstyles.

Reference to attack trail being brighter is here.

Marth's attack trails are much brighter at the tip, making the sweetspot of his attacks more visible than in previous games.

Solution 2:

The knockback and hit lag (the amount of time the opponent freezes in place) will be noticeably higher. The difference is especially pronounced on Smash attacks.

Reference: Smashboards