The previous answer to this question in right on target. I would add one other strategy for your consideration. If you have specific colleges/universities in mind, pick up the phone and call the admissions office and ask them for their dates.
Sometimes the admissions officer will say that applications are accepted throughout the year. This is done in part to keep their options open as the specific higher education institution works to fill all open seats. If you get this response, ask them when they will begin making decisions on the applications received. Based on that information, you should consider submitting your application 30-60 days before the institution begins the selection process.
That depends entirely on the college. Look on their website or call their admissions office to ask: they'll be glad to help you.
Also be aware sometimes the deadline is earlier if you want to be eligible for scholarships and financial aid, and you may want to have college plans together before you turn in the FAFSA in the Spring. If you don't need any of that, a lot of colleges have a "rolling" admissions policy: they accept new students at any time as long as there's room for them, which these days there tends to be plenty.