What monthly or weekly budgeting techniques do you follow and have good results with? Any tricks for avoiding impulse buys?

I go grocery shopping once a month at Wal-Mart & buy what they sell cheaper than everyone else. It’s a 30 mile trip there. Then I pay all my bills by the first day of the month they all clear by the 5th. After the fifth I know exactly how much I will have left over for the month.

I write down every month what the projected bills are for the next month. I add them up and minus from the total I get paid. I also plan any extra purchases that will be made that month. For example buying a vacuum, freezer, baby clothes.. etc…
I get paid once a month the same every month so that makes it easier.
Most of my bills stay the same amount as well.
I plan my budget at least 1-2 months in advance or I try to sometimes things just come up.

My biggest problem I’ve notice lately as well is when I go to the grocery or Wal-Mart, I pick up extra stuff that I didn’t go into the store for. I’ve been sending someone else into the store to buy what I need while I stay in the truck. Also, because I’m like 39 weeks pregnant (LOL). I guess another thing to do would be to use cash. When you leave your home take only a little more than you actually for our purchases.