Avoid the Display Screen:
At the beginning of a match every players chosen character and passive/ultimates are displayed. As a Vincent player, you won't to avoid being seen on this screen. Seeing a Vincent in the display screen does a lot to Vincents initial element of surprise. You're working off of the idea that most players don't pay attention to the slight change of characters that happen at the last few seconds before a match starts. To maximize the element of surprise, wait a few seconds for the match to begin and let the chaos of the gunfight distract from your character change. (Another thing that works in your benefit is that most people don't use voice comms, can't have anyone ruining the fun.)
Kamikaze/ Ninja Vincent:
This tip is for newer Vincent players that don't have the strategy down yet but want to use him for match impact. One of the few things that makes Vincent so difficult to use is the strategy required to make him effective...what makes Vincent annoying is his one-shot potential. The Kamikaze Vincent isn't worried about anyone else except for the problem causing target (usually a tank) and removing them from the fight. You can worry a lot less about fighting numerous enemies and just rush the tank (obviously from an undetected flank or just simply jump/ fall onto them). Will you die, probably, is killing something with 9000-12000 hp with one-shot worth it......yeah.
AoE is not your Friend:
Chemist, Cristina, Kazama are all AoE characters that can make your time very difficult (Especially if auto-fire is enabled on these characters). Try your best to avoid those characters or at the very least, get the drop on them. Also just for the record, AoE stands for Area of Effect, think splash damage or explosive damage.