Examine your reasons for wanting to defer attending college. The college will probably require you to explain your decision, so you need to have a good reason ready. Consider how you want to spend the year. Do you want to volunteer? Travel? Work? (Work on your tan is probably not a good response.)
Investigate which colleges have a supportive deferrment policy. Make sure your top choice will allow you to defer and find out if it has restrictions for doing so. For example, will it allow you to take classes at another school? Will it require you to have a specific plan for the "gap" year?
Follow normal procedures for applying to colleges. Get in your application, references, essays and transcripts on time.
Notify the admissions committee that you want to be deferred after you receive notice of acceptance. Check the deadline by which the college expects to receive the petition for deferment and be sure to get your request in before then.
Send in a deposit to hold your place in next year's class if your deferment application is approved. This deposit may be several hundred dollars.