1. Get the Amazon credit card, and Prime (free unlimited 2 days shipping). When I signed up for the card, they gave me $30. If you get the inhouse credit option, I forget what it's called, they gave me another $30. The card is good because you can spend ANY amount of points and it's 3% points back at Amazon. So you don't have to hit $20 for example, like you do with the Chase Freedom.
If you're a student, check out the student version of Prime.
2. Get Prime and use Subscribe and Save. 5 items that arrive in the same month saves 15%. At one point it was 20% for a promo. They sell toilet paper and it's cheap this way. One less thing to get and bring home from the store. Prime makes the shipping free. At $80 a year, and 5 items a month, that's about $1 per item. But once you have Prime you also get a crapton of benefits like more free music and video. Prime is 'Apple-esque'. Once you have it, how did you live without it? I get a lot of meal bars and protein bars and a bale of TP, and I have creatine on an every 3 month or so basis. You can choose 1-6 months for delivery scheduling and change any time. IIRC the minimum savings for a single item is 5%.
3. Sign up for Amazon Moms. Look for a credit off your next order. IIRC, it has to be a Subscribe and Save order. I got that in an email and IIRC it was $20 or $30 which I more than used. Right now it's 20% off diapers. One more thing less to buy, and Subscribe and Save eligible. And you don't have to be a Mom. They don't check.
4. Finally, support your local blogger. They probably have a search box that you input what you're going to buy in, and it gets them a small commission on something you were going to buy anyway. Shameless plug: http://beachfitrob.com has one on the upper right. Help me or someone else out since it's painless and costs you nothing.