Test preparation

You should first go for the previous year questions, go through NCERT text books, also consider coaching material of Allen and also look up the net for available topics and lectures.

Aptitude tests mostly comprises quantitative aptitude and verbal ability kind of questions.
You can excel quant section by practicing thoroughly. There is no short cut in quant.
You can perform well in verbal reasoning and grammar kind of questions by solving some good verbal books and most importantly improving your vocabulary. My favorite book for vocabulary development is Word Power Made Easy (by Normal Lewis)
For quant, you can solve the book - India's top 100 common sense puzzles.

Hi Sakshi, Early Action as the name suggests, you will be notified of the decisions in a month. Regular and non early action rounds take longer. Make sure you submit your entire application material if you apply under Early Action. Standford's early action has certain norms to be followed, you cannot apply to any other university under Early Action. Check the policy here http://admission.stanford.edu/application/decision_process/restrictive.html and also check the link given by Chetna S. You have time until Nov 1, all the best!

Hi Aditya,
MAT exam is an aptitude test. There is no set or defined syllabus for the exam. It is designed to assess the natural ability of a person towards their desired objective. The MAT Test helps evaluate critical thinking skills which are typically relevant to management positions. Mainly the questions are asked from Language Comprehension, Mathematical Skills, Data Analysis, Intelligence & Critical Reasoning, Indian & Global Environment Section.
For more details kindly refer the link below:
https://www.shiksha.com/mba/exam/mat
Hope it helps. Please feel free to revert.
Wish you luck.