Simple budget for a tight month - what worked for you?

I am $450 short each month and trying to find it. I am in Wichita, in case local advice matters. The rent is fixed and the car payment is high. What helped you?

A paper list of bills by due date helped me more than an app. I could see the month at a glance.

Sell things you do not use. I made about $450 from a weekend of listing.