Warehouse stores: good for bargain shoppers?

We just joined Costco.  I love that place!  Since the twins eat like little football players, it was a good idea for us to buy more items in bulk.  I feel the quality of coupons has gone a bit downhill lately and I haven't been able to stock up on products like granola bars and kiddie type food.  At least at Costco we can guarantee we get a decent price on certain items.  Plus they have the double cart for the girls to ride in, which no stores have around here.   It makes it so much easier to shop. 

You do have to be careful in warehouse stores.  It really helps if you break down each item and see if it is really a good deal.  Here are some quick tips that I have for buying in bulk.

• With any bargain shopping, it is best to know how much is a good price for an item.  Some people keep price notebooks, but I don't have enough motivation for that! It's easy enough to just keep a mental note.  Try to remember sizes as much as you can.  I call these my price points.  It's good to have these mental notes to know when you should stock up on an item.  As always, coupons may vary, so a general price range is efficient enough.
• Example: I know my price point for jarred spaghetti sauce is $0.75, and its usually around 20 oz.  At Costco they have the huge containers for a much better bargain.
• Be realistic.  Can you really eat THAT much before it goes bad?
• We made this mistake with tortilla chips (which we don't buy anymore), and the 2 lb bag didn't stay fresh for long.  Duh!  
• Don't forget to look at their clothes and gift items!
• They have Carter's sleepers for the kids for $7, which is an AMAZING price.  They only get cheaper if you buy them off season on clearance
• Check out the produce section!  
• I found 3 lb packs of cubed squash for $3.99.  At Meijer a 12 oz package is $2.99.  Such a great bargain.  You can steam it, roast it or use it for baby food.  It also freezes well.
• Pineapple and avocados are also cheap.
• Just remember to think about how much you can actually use.  I love the price of the organic lettuce, but there is no way I could finish it before it got soggy.
• The price of batteries and light-bulbs can't be beat.  We got enough energy efficient bulbs for our entire house (about 20) for less than $10!  Batteries are great to stock up on this time of year with kids around.  You can get about 20 for $13.
• Just want to check out the prices?  You can get a guest pass to browse (but you can't buy). I have heard if you don't have a membership, you can buy a gift card and use that to pay.  That is a great idea for someone who may not need to shop there regularly.  You can load up a gift card for $25 and get what you need and pay the difference on a separate card.  I would research this a bit though, because I have just heard this on other bargain blogs.

Do you have any warehouse shopping tips?  I would love to know what you buy!