Don't just grin but smile.
2. Give the customer your full attention when you utter the words, "Can I help you?"
Stop writing. Stop putting paper away. Stop whatever it is you are doing that takes your attention away from the customer standing in front of you.
3. Convey excitement in your voice.
"Can I help you?" can take on so many different connotations depending upon how you say it. Say it with enthusiasm and you can set the tone for the customer interaction.