Here's a tip I learned so very long ago: Never shop hungry.

That being said, I'm really careful about what I buy anyway and plan my purchases so that I end up using everything. Fresh foods can still spoil because I didn't spot a moldy spot, but that's pretty rare. Dried foods are great.

Honestly I have little good advice to give aside from awareness and planning, since I am by nature perfectionist about my food and budgeting and can't relate to the meme.