Ok I copied and pasted the steps from the link. Here is how you do it, you gotta jump through a couple hoops. Take 1 trip to Best Buy and spend around 15 Minutes on Club Nintendo's website. Don't really want to get into a debate about the ethics of this, do it or don't, that's up to you
Step 1a) Buy 3 copies of Mario Kart from Best Buy. The price currently is $60, or $48 for those with a Gamers Club Unlocked Membership. Don’t worry though, Amazon currently has the game priced for $48.80, get Best Buy to Price Match this if you don’t have GCU.
3 Copies of Mario Kart 8 at $48.80 = $146.60 BEFORE TAX (*$144 if you have GCU membership)
Step 2a) Open your 3 copies of Mario Kart 8 take out the Club Nintendo registration codes, and trade them back into Best Buy (you currently receive $40 credit per copy…$44 if you have GCU).
Trade- in Credit for the 3 Copies of Mario Kart 8 = $120 (*$132 if you have GCU membership)
Step 1b & 2b) The same basic idea, but you would buy 1 copy, open it, and then trade it in. Using your $40/$44 trade in credit to buy your 2nd copy. Then you open that, trade it in, and use the credit to buy your 3rd copy. This way you’re only required $70 or so (after tax) cash in hand to buy your initial copy, and your end result is $$40/44 in trade-in credit instead of $120/$132
Step 3) *Ignore this step if you’ve already purchased a personal copy of Mario Kart 8 for yourself, or if you don’t want Mario Kart 8. Use your trade-in credit and now purchase your copy of Mario Kart 8. Best Buy limits the GCU to only 3 copies of the same SKU, so those using the GCU membership might not be able to buy a 4th copy at $48. If that is the case, this is when you use the Amazon price-match. For those using the Amazon Price-Match for the previous 3 copies, I’m not sure how many copies they limit a customer to when performing a price-match. The way around this would be to just ring up different transactions, or just order directly off Amazon and hope that Best Buy’s trade-in value doesn’t go down before you receive your copies.
Step 4) Go to club.nintendo.com and create/use your main account. Then create 3 (2 if you didn’t buy a personal copy) other accounts that you will add to your family. This is explained here on their support site.
Step 5) Register all 4 (3 if you didn’t buy a personal copy) and then select a different free game for each one. Write-down, save, copy, etc your Redeem Codes.
Step 6) Boot up your Wii U, go to the eShop and select “Download Code” at the top of the eShop menu. Enter in each of your codes individually and you should end up with all 4 digital downloads. *If you don’t have a Wii U yet you can hold onto these codes until they expire, but I’m not sure when that exactly is. If you order a refurbished Wii U and are waiting on it to ship to you, you should be fine if you redeem it when you get your Wii U.
Summary) Following Steps 1A & 2A You will spend roughly $146.60 + TAX on purchasing 3 copies of Mario Kart 8. You will then turn that $146.60 + TAX into $120 ($132 if you have GCU) Best Buy Store Credit PLUS the 3
Redeem Codes. If you do Steps 1B & 2B you’ll spend $48.80 + TAX initially, and then $8.80 on each of the other 2 copies, costing you $66.40, turning that into $40 store credit PLUS the 3 Redeem Codes (GCU Members Spend $56 and end up with $44 store credit) .
If you follow Steps 1A/2A or 1B/2B depends on how much it bothers you to turn cash into store-credit, and/or how much of a hassle it is for you to break things up into several transactions.
You then use your remaining store credit on the final copy of Mario Kart 8, which you keep for yourself and gives you the 4th Redeem code. Or you can just keep the credit for another time.
BONUS) If you have a Deluxe Wii U and are part of the Digital Deluxe Promotion you will receive Reward points for every one of these “free” purchases. The points should go Wii Party U (399), NSMBU (499), Pikmin 3 (599) and Zelda Wind Waker (349). Which is 1846 Points. You get a $5 giftcard for every 500 points. This means you’ll receive $15 in Nintendo eShop Giftcard and be 144 points away from another $5 (This might be incorrect, but I believe when you use your $15 eShop Giftcard, that will be another 150 points).
MORE BONUS) If you’re a Best Buy Rewards Member you should receive 2x points for every video game purchase. That means you’ll receive 96 points for every Mario Kart 8 you purchase. If you purchase 3 that’s 288 points, 4 copies would be 384. $5 Reward Cards are rewarded for every 250 points. You earned another $5 in Best Buy Store Credit
SIDE BONUS) The Gamers Club Unlocked Membership is currently on sale for $60 for a 2 year subscription. This gives you 20% off all new game purchases and 10% extra in trade-in. This will pay for itself if there are 5 games you plan on buying at $60 MSRP in the next 2 years.
FINAL RESULTS) Those who haven’t purchased Mario Kart 8 for themselves yet will spend roughly $75 for a personal copy of Mario Kart 8 and all 4 Digital Downloads (some of the Wii U’s best games), $20 in eShop Store Credit and a $5 Best Buy Reward Certificate if you follow Steps 1B & 2B. Steps 1A & 2A would result in you spending around $150 and recieiving Mario Kart 8, All 4 Digital Downloads, $20 in eShop Store Credit and $120 in Trade-in Credit ($132if you’re a GCU Member) and a $5 Best Buy Rewards Certificate.
If you already own Mario Kart 8, you’re looking at spending around $65 and getting the other 3 Digital Copies, $15 in eShop Store Credit, a $5 Best Buy Reward Certificate and $40 ($44 if you have GCU) in Store Credit. That’s turning $65 cash into $60 in random credits ($64 for GCU) plus getting all 3 Digital Copies