Most novice lifters are aware that lifting belts can be a helpful tool for safety when training heavy barbell movements. There is a misunderstanding, however, that a belt acts like a back brace and should be tightened as much as possible to create support for the low back.
This is NOT how a belt should be worn and NOT the purpose of wearing a belt!
A belt is a tool to enhance proper breathing and bracing. Belts should be worn loose enough to fit a couple of fingers between your belt and your ribs -- if they are any tighter, you can not take a proper diaphragmatic breath and therefore you are unable to brace your core as effectively and efficiently as possible. Another common error is wearing your belt too high along your trunk to properly support your abdominal pressure. Remember, the diaphragm lives parallel to the bottom ribs and releases down and out when the lungs are inflated. Think of your bubble of abdominal pressure being shaped like an oblong balloon. If you wear your belt too high along your ribs, you are just cutting your balloon in half and creating a weak point for undesired instability instead of supporting your abdominal pressure from below the diaphragm to reinforce a strong brace.
The final recommendation to ensure you wear your belt correctly is purchasing the proper size and thickness. Belts are most commonly manufactured in 4" height, 3" height, and 10mm or 13mm thickness. There are many great brands out there but you want to be sure the height and thickness make sense for your proportions. Measure the distance from your bottom rib to your hip tip to find which height is best for your unique anatomy and select a thickness that feels supportive yet comfortable.