Oh shit, I've been a Costco member for more than 30 years. Even coasted for a decade as a free family member on my brother's employee card when we were both single. I second everything Happy Plant has said. They will pry my Costco Card out of my cold, dead hand, hopefully at least another three decades from now.
I saw that deal on Living Social and experienced brief twinges of envy for all the potential new Costco members. I knew many clever mustachians would figure out ways to work the angles to score that deal.
DIY Costco Vanilla has become a huge money saver for me, as I use it frequently. I just noticed the Costco size bottle has somehow zoomed from $6.99 to $27.99, WTF? Meanwhile, the Kirkland 1.75 liter bottle of Vodka has held steady at $13.99 and they seasonally, but regularly, carry twin packs of Rodelle Whole Vanilla Beans, at a price I can't remember off the top of my head, but is way cheaper than anywhere else, including the internet. Open the vodka bottle, split open a whole tube of beans lengthwise, drop 'em in, hide the bottle in your pantry, and you're on your way to cheap, awesome Vanilla deliciousness. Turn/shake the bottle occasionally and wait a few months. Voila! 1.75 liters of yummy Vanilla. Great for gifts, but start soon if you want it ready in time for Christmas. BTW, anyone know the reason for the huge price spike? I even double checked the shelf tag, sure I was just looking at the wrong one. Nope.
Back on topic, I use a list on my phone. Nothing fancy. I just put an X in front of the items I need to buy, which makes shopping and avoiding the budget bombs a breeze. I leave the Xs until the next trip to help me remember what I bought last time that might be in the outside pantry, oof.
My Costco is one of the Top 10 in the country. It is always a madhouse. I pass the time in line by playing otherwise time-wasting games on my Android phone, completely guilt-free. I am also friendly with the staff, which has proven helpful and makes the trips more pleasant. DH and I laugh laugh laugh when we visit other Costco warehouses in our travels. We shopped in Parker, CO, last month. We were asked if we needed any assistance so many times we thought we were being spoofed. Parking? Checkout lines? Nah, piece of cake.
There have been many great tips so far, but the BEST reason to shop Costco is because they pay a living wage and provide good benefits, including solid healthcare, to their employees. This alone is enough to justify the Costco membership, IMO, because it reminds me to shop there and support a retail giant who actually treats their employees like valued human beings who have worthwhile lives and families to support, instead of like so many clods of dirt.
And gas, for that tiny number of Mustachians who still possess gas or diesel powered vehicles. Ahem.
Whew, I guess I had a lot to say on that subject!