The best time to start the preparation for JEE Advanced examination is typically after the declaration of JEE Main result and eligibility criteria. This is because the eligibility criteria for JEE Advanced are based on the performance in JEE Main.

Once you have determined that you are eligible for JEE Advanced, you can start preparing for the examination. Typically, students start preparing for JEE Advanced after the completion of class 11th or at the beginning of class 12th. This allows students to focus on the advanced level of mathematics, physics, and chemistry, and build a strong foundation in these subjects.

Starting early also gives students enough time to go through the entire syllabus, practice and revise important topics, and familiarize themselves with the exam pattern and question types. Additionally, students can also take mock tests, solve previous year question papers, and attend coaching classes or online tutorials if they wish.

It is important to note that JEE Advanced is considered to be one of the most challenging engineering entrance exams in India and requires consistent and dedicated preparation. Starting early and following a structured study plan can help students achieve their goal of securing admission to IITs.