Tips for 400m sprint?

Hey, i have been entered for a 400m race next week! I used to sprint 200m and 100m a lot, but i havent trained or ran a lot this year. i have never run a 400m and am a bit worried and would really like to do well. I know i havent got long but does anybody have any tips about pacing for the race? or diet and good training/excercises in the lead up? what is a good time to aim for?