The only piece of equipment you really need to go orienteering is your brain.
However, the following may be useful:
Watch
Helpful for checking your time since there are time limits on orienteering courses.
Compass
Helps you orient the map to North and take bearings. You can also rent one for $2.00.
Suitable Footware
Light hiking boots or running shoes.
Clothing
Dress as you would normally for a hike that might take you through some brushy areas.
The beginner's course (white) generally sticks to trails, but other courses may go
through fields and forests.
Water/Snacks
Water is almost always available, but you might want to bring your own for
convenience and to drink on the course.