I was a cashier at PetCo for awhile.

JUST REMEMBER: if you were in line being checked out, how would you like to be treated???

I know when I'm in line and the checker doesn't even talk to me, make eye contact, or try to strike up conversation it just... bothers me, and makes me feel very uncomfortable. ALWAYS smile, ask how their day is, if they found everything alright, just make small talk!! You have no idea how just small talk can make someone's day just a bit brighter. I found it was easier to talk to my customers while at PetCo because we had something in common -- pets! And if you got the customers talking they would talk FOREVER. And they LOVED when you asked about their pets, I mean come on, everyone loves talking about their pets. Hehe.

So I guess, if the customer is buying an item you've used or are familiar with, tell them "OH this was a great choice, I use this and it REALLY WORKS!" or something like that, make them feel HAPPY for making the choice they made lol. Sounds lame but it helps.

OH and don't stress out about having to learn register, its SO EASY.

EDIT: OH someone brought up a good point. AS SOON as you hand a customer their change -- CLOSE THE CASH DRAWER. Then if they try telling you that they gave you a twenty and you gave them wrong change, you HAVE to call a manager over, they will count your drawer, and if it is off then the customer was right and they will get the appropriate change. BUT if its correct, the customer was lying, and your managers will deal with them NOT YOU. So NEVER give someone change for what they SAY they gave you ALWAYS ALWAYS ALWAYS call a manager. ESPECIALLY around Christmas.

OH one more thing -- always ASK if they want their receipt in the bag or not. Don't just assume to stick it in their bag. If they're really busy put it in the bag but TELL THEM "your receipt is in the bag, sir or ma'am". Usually I would hand them their receipt if they used their debit or credit card but stick it in the bag if they paid with cash. But its always better to ASK. Because I had a customer chew me out because I put it in the bag instead of handing it to him ON MY FIRST DAY.