1. NEVER wear suspenders with a belt. You don’t wear contact and prescription glasses at the same time, right? Belts and suspenders serve the same purpose, to keep your pants up. No need to double up!
2. Vest or suspenders, but not both. Suspenders are a sharp accessory you want to show off which will not happen if you are wearing them with a vest.
3. Proper placement is key. Suspenders should fall straight from your shoulders to your waist. If you see / \ or \ / happening, readjust.

https://www.youtube.com/watch?v=FTbpuIlHWrc