Lots of good advice above. I've had sales training and want to re-emphasize the comments above to (1) LISTEN to customers, (2) be honest and (3) know your product. If you don't know, tell the customer you will find out. I just bought new wheels. Went to one LBS and they showed me some wheels and the guy there said he "thought" they were about $650. I looked them up online, they should have been about $360. Was he BSing me or did he just not know? I prefer to think the latter, but nevertheless I just bought new wheels at a different shop.
Also, if you are with a customer on the floor, at the register, whatever, do not let another employee distract you from the customer until you are done. Congratulations on the new job!