I agree with JNH14! Don't wait for your associate teacher to tell you what to do! Jump right in and help out. Introduce yourself to the kids and make sure you're firm. Remember you're going to be their teacher and not their friend. Prepare for the lessons but don't over prepare. Learn all the routines - especially at that age, routines are everything. Good discipline means consistency and it's easier when you learn your students' names quickly. Don't make things too complex - simplicity is the key. Remember to bring your own personality into your teaching - follow your supervisor but you can't mirror everything he/she is like.
You'll have a wonderful time! You'll going to remember some of the things the kids say to you!
Here are some of my favourite students' sayings (my former grade 1 students):
"I have a big headache from looking at words all day."
"When I grow up I want to wear your orange vest and do recess duty."
"I can't get my snow pants on!" (This was in April with 70F weather)
"I just spit on him a little bit."