The grocery store on a Saturday is daunting in many ways. Screaming kids... long lines ... the sample lady giving out chips and dip ...
But I find the aisles of my grocery stores are a lot less tempting these days when I stick to a few simple rules:

Always take a list. I make a list that I add to all week long instead of sitting down right before I leave for the store trying to remember everything. It's easier to track the things you truly need when you write them down as you run out. Sticking to the list once you get to the store is the true key.

Stick to staples. It's easier to not fall for those buy-one-get-one free cookies when you stick to the things you truly use on a daily basis. It's also less likely you'll find treats you've never purchased before when you're focused on getting "must-haves" instead.

Stick to a budget. By working out your budget before you go you'll find you're more likely to spend yours on the things you really need rather than things you want. My trick is to leave my debit card at home and take only as much cash as my true staples require.

Shop on the edge. The healthiest foods are located on the perimeter of the grocery store. Fresh fruit ... veggies ... meats ... dairy. When you get into the heart of the store, that's where the sugary cereals, candies, and cookies lurk. Spend most of your time on the edges of the store and you'll shop smarter.

Never shop hungry. That one speaks for itself!