Application for higher studies : When to start ?

You should start your preparation for applying for higher studies when the seeds of the desire to pursue higher studies are sowed in your mind :)

A Realistic time-line for application:
For those who want to pursue higher studies immediately after completing their 4-year undergrad course, the best time to start your preparation process is by your 6th semester. If you are planning to enroll for Fall 2012 ( 1st semester starts roughly by Septemter 2012), the right time to start your preparations is by Jan 2011 (i.e. 1.5 years or 18 months in advance). For Fall admission most universities will start the application process by September the previous year and the typical application deadline varies from December to February mid.
(Note: Chances of getting Financial Aid is far higher for Fall admissions than for Spring Admissions). A more commonly followed time line for preparation is given below.

12 Months to application deadline

Research academic programs

Research on which grad schools to apply and their deadlines

Identify 3-4 recommenders (For Referee reports)

Start Preparing for TOEFL and GRE and register test dates

6 Months to application deadline

Take GRE and TOEFL exams

Talk with your Referees and supply them necessary data (Give at least 1 month time for them to prepare)

Prepare your Resume

Prepare Statement of Purpose (SOP)

2 Months to application deadline

Get your Referee reports ready

Revisit SOP and Resume for improvements

Start online application process

Mail official transcripts

Note:

While the identification of semesters among universities differ slightly, the common way of identifying semesters is as follows

Fall Semester : September - December
Spring Semester : January - May