Skip down to Setting Up Your Account if you're in a hurry and just want the bonus for Checkpoints. If you're interested in learning about other money-making opportunities read on.
Combining the below apps I've made a few hundred in gift cards and cashouts with PayPal (actually a few thousand if you count referrals). The trick is to maximize your time and purchases. For example, you can get points on Checkpoints and Shopkick for walking into a single store. Then, you can get bonus points on each app for scanning the same items twice.
Some apps also reward you for making a purchase. The three below are great because they all give you a post-purchase rebate, which is like a mail-in rebate without the annoying mailing in part. You'll notice that companies will offer run campaigns to promote one of their products and it'll appear on multiple apps at once. That's when you want to take advantage of the deals and get free items, or even get paid to shop.
Say you want to buy a Naked Juice smoothie. Right now Ibotta gives you $1 back, Shopmium gives you $1 back, and Naked Juice has a $1 coupon on their website. Sometimes at Whole Foods Naked Juice is on sale for for $1.50 each. If you use the coupon and get the two rebates you'll be making $1.50 and getting a Naked Juice (which are pretty tasty and healthy).
For both apps you just have to scan the product's barcode then scan the receipt and the money will be added into your account. Be sure not to throw out the proof until they process! Or, if you're going to throw out the product take a picture of the barcode and email it to yourself, you can scan the image off your computer if need be and then scan the receipt again. Usually they'll register the first time but if the images are blurry or the receipt is crumpled and hard to read they may ask you to resubmit.
Check Into Stores and Earn
CheckPoints - Obviously the app that brought you here. Check into stores with your smartphone and scan items to earn points. Cash points out for gift cards at a variety of stores (including Amazon), or earn frequent flyer miles, donate to charities, or exchange for products. Use code BonusCode2013 to get free points when you register.
Shopkick - Little different since it's not groceries but you get points for walking into a number of different stores, mostly electronics, clothing, and home goods (e.g Best Buy, American Eagle, and Crate and Barrel). Earn extra for scanning items or making a purchase with registered credit card. This is great if you're at a mall where you can easily earn a few dollars while walking around. Cash out for gift cards ($5 minimum).
Use These Three When Grocery Shopping
The below apps all act similarly and can be combined for great savings or even earnings. You buy an eligible product and then scan the product's barcode and the receipt and they deposit money into your account! The best part is you can use the same receipt and barcode over and over again, and because these are all post-purchase rebates you can stack them with coupons.
Checkout51 - Get cash back for buying groceries or home goods (cleaning products, shampoo, etc.). They rotate new products every week and usually offer 2-3 deals for cash back on essentials like milk, tomatoes, or bananas. You earn $.25-$1.50 for each item your purchase and withdraw your money via PayPal once your account reaches $20.
Ibotta - This is a quickly growing app that started with groceries and home goods but they've been adding clothes, alcohol, movies, and a few other categories lately - even some online shopping. Cash out via PayPal or for Starbucks, iTunes, Regal Cinemas, or Whole Foods gift cards once you reach $10. Ibotta recently introduced team bonuses. Build your team by inviting friends, or use the link here to start with one friend (me).
Shopmium - Like the above two, buy groceries and scan the receipt. Shopmium says they have unique offers but sometimes they match offers from the other apps. Pays out in PayPal and no min for payout! Use code YAAYECRC when you register to get a you free Lindt chocolate bar.
Scan Receipts (again) and Earn Even More
Receipt Hog - Get points for scanning your receipts from grocery stores, superstores, pharmacies, dollar stores, pet shops, and even beauty supply shops. Each receipt has a really low value (a few cents to a less than a cent per receipt) but you have the receipt anyway anyway and it only take a few seconds. Cash out for Amazon gift cards or through PayPal.