Students who apply for early decision can be "deferred." This simply means you did not stand out enough to warrant the college offering you admission in the early decision process. It could be any number of things that forced the admissions office to make the deferral decision, but all the office is doing is putting you in with the regular applications. Because early decision usually requires higher scores on the SAT and a better GPA it is likely you will stand out during the regular applicants but there is no guarantee.
Being waitlisted means the college is not denying you, but currently there is not room for you on the roster. Just like students apply to a number of different colleges, colleges accept more students than the facility can handle based on a standard refusal rate for the college. Once the university feels it has offered as many slots as will be open in the fall, taking into account the amount of students likely to go elsewhere, the admissions office begins wait listing candidates who barely did not make the cut. This means if more students than expected decide to attend other universities, you will get a spot.
If you are differed, you actually have a few tools at your disposal. You know the university remains interested in you, otherwise the admissions office would send a rejection. This is the time to find any advocates you can. If your high school advisor knows you well, a character reference or phone call might be in order. If you know any alumni to the school, a call or letter of recommendation could tip the tables in your favor.
If you know your scores are decent but not extraordinary, get your application in early. Depending on the competition, the acceptance rate can go down as the application process continues. The admissions office often adjusts scores upwards if the college is receiving more applications than normal. Be sure to decide whether you really want to be on the "waitlist." You have to respond to the letter, but you must take into account your options for housing and financial aid. Call the college and find out how the list is ranked and where you sit. This gives you a better idea on your chances of acceptance. No matter what, look into your other education options such as taking courses at a community college for a semester.