It is never too early to start thinking about when and where you intend to apply to graduate school. Applications for a given year are usually due before the end of the of the previous academic; usually December, 1 or March, 1. Design your program of coursework and research so that you have completed your statistics, laboratory, advanced seminar, and at least one semester of research experience by the time you apply (Fall). You should also have taken your GREs before applying.
You should have taken your General and Psychology GREs by Fall of the academic year during which you apply and achieved satisfactory scores.
When is the best time to take it? Most students take it during the Fall of that year that they apply. Although the General GRE can be taken at any time, students find that it is best to take the Psychology Subject GRE after they have taken Introductory Psychology and a course in each of the Groups (Group I-III). If you are not able to take a course in one (or more) of the 3 Group areas before you take the Psychology GREs, try to read through an introductory textbook in that area. The practice GRE books are also very helpful.
What is a satisfactory score? Graduate programs/schools will often state their GRE cut-off (minimum score), as well as the average score of accepted students, in their school bulletins and catalogues. Use these as guidelines. Sometimes students with below average scores will be considered if the rest of their application is strong.
The General GRE now can only be taken on computer at designated ETS testing sites. The 'up-side' of this is that you can take the test once a month (if necessary) and the testing schedule is fairly flexible. The 'down-side' is that when you are taking the test you can't go back and look over your answers and your maximum score is heavily influenced by your performance on the first few questions. For this reason it is important to get some familiarity with the test format before sitting down to take it, particularly if you don't like working on computers. Make sure to time yourself when you are taking practice tests.
The Psychology Subject GRE is required by most, though not all, graduate schools. It is a good idea to take it on a different day than the General GRE or else you will be exhausted. The Subject GRE is paper-based and is only offered on certain dates.
Letters of Recommendation
Letters of recommendation are a very important part of your application package. Most schools require a minimum of 3 letters. Optimally, these letters will be from research faculty in Psychology. You can supplement these 3 letters with additional letters from professors in areas outside of Psychology or work supervisors (if you have been out of school and working for a long time), but your primary 3 letter should be from faculty or researchers in a Psychology or Psychology-related discipline.
Whom should I ask? The best quality letters come from faculty with whom you have done Research. If a graduate student or post-doc is primarily supervising your research or internship, this is not necessarily a problem. Faculty will often sign or co-sign letters written by a trusted graduate student. Furthermore, if you have participated heavily in lab meetings and had some meetings with the professor directly, he or she will often write the letter him/herself (with consultation from the graduate student who may have even more extensive contact). If it looks like you will primarily be working with a graduate student, see if you can arrange to meet the professor once or twice a month, possibly together with the graduate student, to discuss the project. Advanced seminars sometimes also provide the level of personal interaction necessary to get a good letter of recommendation (especially if you get a good grade). Generally, large introductory courses do not and many of these professors will not write letters for you unless you really stood out in class, came to office hours very regularly, had intense philosophical discussions with them, etc.
NOTE: Ask your professors well in advance of the application deadlines if they are willing to write you a letter - at least 1 month and preferably 2 months in advance. If that person says no, you will have more time to find another person. If that person says yes, it is best for the faculty member if you can prepare all the recommendation materials and given them to him/her at least 1 month in advance of the first deadline.
What do I need to give the recommender? Preparation of the materials means that you have included all recommendation forms with as much of the information on the form filled in as possible (i.e., all names and affiliations, whether you waive your right to see the recommendation) together with an addressed, stamped envelope for each recommendation. If a school does not provide a recommendation form, just include an envelope and instructions that mention there is no form attached. It is also advisable to give your recommender a separate checklist sheet clearly stating the deadline for receipt of each letter. Ask the recommender to notify you when he/she has sent the letters.
Clinical Ph.D. versus Psy.D.
If you are interested in Clinical Psychology, you will have to decide whether to pursue a Ph.D. or Psy.D. degree. Other areas of psychology only have Ph.D. programs. Sometimes you will find that Ph.D. programs are often referred to as "scientifically-oriented" whereas Psy.D. programs are "professionally-oriented." Generally speaking, the Ph.D. program provides training in both clinical research and practice, but may be more heavily weighted toward research. The Psy.D. programs are more oriented toward training students for practice in clinical and other applied professional settings and research is often less emphasized.
These different orientations are reflected in what these programs are looking for in applicants. Ph.D. programs want to see research experience. Psy.D. programs want to see internship experience.
In some ways, the Ph.D. degree provides you with maximal flexibility because you can pursue a career either in research or practice, whereas the Psy.D. limits you more to practice. On the other hand, Psy.D. programs are often shorter and provide a broader internship/externship experience. Finances are also a concern for many students. Ph.D. programs tend to provide funding for their graduate students while Psy.D. programs tend not to provide funding. Finally, Ph.D. programs tend to be somewhat more competitive than Psy.D. programs. You should choose the program that best suits your needs and interests. Practically speaking, many clinically oriented students apply to both Ph.D. and Psy.D. programs.