Experienced orienteers who intend to run fast wear special studded shoes, like stronger versions of cross-country shoes. But any kind of running or walking shoe will be OK to start with. Shorts and T-shirt are OK for parkland events, but most orienteers wear full body cover for forest and farmland venues. If you choose to run as a group and use only one map, or run more than one course, you pay for only one entry. Club members pay a little less.
Every event offers courses of different distances and with different technical challenges.
The longest course at major events is usually designed for skilled athletes who are prepared to spend an hour or two in the forest. However, the shortest course is designed specifically for 10 year olds, who will take 40 minutes at the most, usually less than 30 minutes. You and I can run on one of the courses that fit in between. You will need to fill out a clipcard, and perhaps copy your control descriptions on to it, then hand over your money and register. You will be given a map.