Answer
Search the retailer name, open its store page and compare the listed codes and deals. Start with offers that match your basket and have a future or current validity date.
Do not choose only by the headline percentage. A smaller discount can be better when it applies to more products or has a lower minimum spend.
What to check before checkout
Read the retailer’s current promotion terms, confirm that the code applies to the items in your basket, and make sure the expected saving appears before you pay.