I told my DD a few weeks before and kept reminding her about it or she would ask me questions about them,
She wanted to know if they would hurt, why she had to have them etc
I was completely honest and said yes they would hurt but only for a few seconds and then it would be okay.
We pinched each other so she could get a bit of an idea what it would be like etc. She would get upset about it sometimes and cry but the closer it got she didn't get upset at all.
On the day she was actually quite excited about it and was really good with it all.
As a special treat we went to a near by party shop and she chose some helium balloons, three of them i think and that totally made her day along with the purple bandaids the doctor put on her legs.