This is prompted by a quick trip (that became not so quick) I made tonight... Here are a few tips so you don't become that person.
1) That's great that you have 10 coupons for 1 particular item. Use them all. Just don't wipe the stores' shelves clean. If the store has 50 of the item, fine. Just don't be that person everyone else hates because they need 1 and can't get it because you've got 10 in your buggy. Make two trips.
2) If you think what you're doing might be sneaky, it probably is. Don't do it.
3) If the cashier looks like they've never seen a coupon before or it's their first week, find another lane. Yes, they have to learn, but not by being bombarded.
4) If you get in lane with said cashier, do NOT start telling them how to do their job. Then when they call over their manager to help them, do NOT tell them both what to do. It just annoys everyone.
5) Pay attention to your purchase. As in, make sure everything you're purchasing has been rung up. The person behind you has been waiting patiently, don't make them wait longer on your separate transaction on the item you weren't paying attention wasn't rung up.
Follow these rules and no one in the store will be annoyed by you!