What is the Right time to start preparation for GATE exam???? Will you please give me some tips for the preparation of the examination??????????

There is nothing like Right time to start preparation for GATE exam, as earlier as you will start preparation you will get benefit of it. I would suggest you to start preparation from the first day of your engineering college because in GATE examination questions come from 1st year of engineering to last year of engineering. Following are some good books which will prove useful to you while preparing for the examination:

Matrices AR Vashistha
Differential Calculus Shanti Narayan
Differential Calculus Golden Series
Integral Calculus Shanti Narayan
Vector Analysis Schaum’s Series
Vector Algebra Golden Series
Vector Algebra AR Vasishtha
Numerical Analysis Golden Series
Numerical Methods S S Sastry
Integral Calculus Golden Series
Vector Calculus Golden Series
Vector Calculus AR Vasishtha
Calculus Thomas Finney
Differential Equations Golden Series
Differential Equations ML Khanna
An Intro. to Ordinary Diff. Equations Earl A Coddington
Numerical Methods BS Grewal
Advanced Engineering Mathematics Erwin Kreyszig
Higher Engineering Mathematics BS Grewal
Engineering Mathematics NP Bali
Probability and Statistics Miller and Freund
Fundamentals of Mathematical Statistics VK Kapoor
Engineering Mechanics Singer
Applied Mechanics Khurmi
Engineering Mechanics Tinua Shenko
Mechanics of Materials BC Punmia and AK Jain
Strength of Materials S Ramamrutham
Strength of Materials Schaum Series
Theory of Machines Rattan
Theory of Machines RS Khurmi
Theory of Machines PL Ballaney
Theory of Machines through solved problems JS Rao
Theory of Machines Thomas Beven
Theory of Machines Sadhu Singh

Following are some good tips which will help you in cracking the examination:

Mentally see yourself succeed
Understand GATE
Concentrate on the syllabus
Prepare a timetable
Follow the timetable
Concentrate on concepts
Make notes
Take mock tests
Check if you are on time
Make more time for yourself