I aim to get as close to $50 dollar increments as possible. This usually means I shop twice or three times a month, $50 each time. I also shop at the farmers' market twice a week on the walk to school and about every other month, do a large bulk-food shop at Amish stores out in the country.
For the grocery store, I keep a running list and start planning a shopping trip when I think I can hit $50 and can do it without kids.
I never take my kids grocery shopping. Never.
Even though I look at the store circular and my coupons before I go to the store, I still have to concentrate and make decisions on the spot, and kids would distract me.
I only take my kids on short errands when I have a short list and know exactly what I need so I don't have to make decisions with kids milling around me. That is probably my biggest thrifty tip for shopping! (And I realize not everyone can work their schedule that way, but I'm sure they have their tricks for making the shopping work with kids).
I also look at my calendar before I go shopping to see what events are coming up so I know if there's anything I should stock now or seek on sale. I'm grateful to have a large pantry and freezer space so that I can take advantage of good sales.
I carry my grocery list and coupons clipped on a little clipboard I made out of cardboard and a binder clip; I used to get so annoyed with trying to use my hand as a hard surface under my list to cross items off my list.
Also, since I am trying to get just over $50, I keep a running total on my list as I put items in the cart, so I'm writing on my list frequently. The clipboard is a wonderful help. Sometimes, I have to put some items back when I get close to $50 because there are some necessary items on my list yet and those other things will just have to wait until next time.
I also try to go shopping when I have the energy and time to not only go through the store and checkout, but also to deal with all the putting-away at home. On a good day, I even get the cloth bags back out to the car trunk.
I would love to hear how you grocery shop! I'm sure we can pick up tips from each other.