12th Grade

August of Senior Year

Start on your Common Application, because it opens on August 1st.
Check in with the teachers who are writing you recommendation letters. Make sure they know the deadlines.
Begin looking at/thinking about essay prompts (all college applications should be released by now).
Find out due dates and processes for scholarships you want to apply for.
Figure out if you want to apply Early Action (non-binding), Early Decision (binding), or Regular Decision.
Make a schedule of application deadlines (some early action apps may be due as soon as Oct. 15th).
Have someone (or multiple people) look over your Common Application essay and finish filling out the Common Application (this will take the longest compared to other college applications).
Check your test scores. If you want to take a test again, register now for a test date in September/October (most colleges say the October SAT date is the last one they'll accept scores from).

September of Senior Year

Schedule a date to meet with your counselor. You will need to talk to them about where you are applying and what scholarships you are interested in applying for because you may need to get a recommendations letter or information about the school from them. You also need to make sure that you will have all of your credit requirements filled so you can graduate.
Fill out a "brag sheet" and send it to your counselor and teachers (they will use this to write you any recommendation letters).
Work on/finish the Common Application.

October of Senior Year

Send test scores/transcripts to schools you are applying to, even if you haven't sent in your application yet (it may take 1-2 weeks for colleges to receive the scores).
Work on/finish the other school's applications that are not on the Common Application.