Ideally, rising seniors should start the school year with their essays already written; this is the best way to ensure that they will not be overwhelmed by the rest of the application process. The great bulk of schools accept the Common Application, which offers 4 essay choices each year, so completing one of these essays is the way to go.
I work with students from brainstorming to editing on these essays, helping them to articulate the best topics and guiding them through the vagaries of pre-college writing. When I work on college essays with students, it tends to take a substantial amount of time, but every student I have worked with has ultimately been thrilled with the finished product.
One thing that I think it is really important to understand about the essay is this: if you have an incredibly solid application (good grades, decent board scores, solid extracurriculars), then it is unlikely that your essay will actually keep you out of the schools you want to attend. However--and this is critical to remember--while a mediocre essay is unlikely to break you, a superb essay can overcome any flaws in your application and actually get you in to places you might not expect.
When I think about what gets a student into college, it is a three-fold set of criteria: your transcript/school career (including extracurriculars); your board scores (SAT or ACT); and your essay (along articulate answers to supplementary questions. Do not underestimate the power of the college essay.
Once we have at least a draft of the essay, I can identify or confirm which schools are appropriate reaches, safeties, and so on. I think that it is important to have a list of a minimum of 6 and an absolute maximum of 12 colleges; this should break down into about one-third safety schools, one-third reach schools, and one-third likely schools.
I am familiar with the acceptance rates of many of the better-known schools, and I can help students craft their college lists in such a way that they would be happy to attend any school on that list. I advise students to start thinking about this list at least as early as the summer, but they should have a final list no later than September, just in case they decide to apply Early Action or Early Decision.
The difficulties in putting together a realistic and exciting list of college usually fall into one of two categories: some students want to apply to as many colleges as possible, either because they are interested in all of them or want to ensure that they will get into at least one; other students get their hearts set on one or two colleges and don't even want to think about looking anywhere else. In the first case, this usually results in tremendous stress and difficulty; trying to give too many school sufficient care and thought is over-whelming. In the second case, it's dangerous to put all of your eggs in one basket; the trick is to help such students find safety schools that they would actually be excited to attend.
Parents, this is a fight that you are going to have trouble winning; let me take it off your hands. I can explain why neither of these approaches work, and help your students figure out the best strategy for selecting their potential schools.
Once the essay is drafted (it can always use more polishing), and the colleges are selected, the actually process of filling out the applications must get underway. This can be stressful, because, contrary to popular belief, the generic essay is usually not the only writing a student has to turn in on an application. Many, even most, schools also tack on supplementary questions. Some of these deceptively simple: "Why do you want to attend our school?" But beware, because it is very easy to undermine your chances by giving these questions short shrift. Consider this: admissions officers read answers to the same questions day in and day out, so the goal must be to elevate the quality and content of your answers to even the most generic questions. Other schools have more complex and thoughtful supplementary questions, and these, too, are important and often daunting. I can offer guidance and resources for how to go about answering these questions, how to strike the right tone and attitude, and how to make students into the best possible candidates for admission into their desired schools.
Perhaps the most important service that I can offer students is a written schedule, which lists every college to which they are applying, along with a deadlines, a potential schedule, and checklist of every single item they must complete for each school to turn it in each application (including the essay, the basic application questions, and the supplementary questions. I have found that seeing it all laid out in writing meaningfully reduces anxiety about getting everything done.