As you want to get the details of preparation tips for the exam of GATE so here it is for you:

Candidates must solve questions in not more than 8 steps

Candidates must solve last year question papers as much as they can

While solving the problem, students must have balance between speed & accuracy.

Candidates must have keen eyes on his performance

In the last days of preparation, if you have any doubts about any topic/formula, you can have a look on these sections. Always remember, more doubts lead to more concept building.

Leave all the books few days before the exam. Have some good time and relax.

Here for your reference I am giving you the list of some of the best reference books for GATE Mechanical Engineering:

Fundamentals of Classed Thermodynamics-Van Wylen

Heat Transfer-Gupta Prakash

Heat and Mass Transfer-R. Yadav

Energy Conversion-Sukhalmoy

Environmental Pollution Central Engineering C S Rao

Surveying and Levelling-T P Kanetakar

Heat Conversion-Arora & Kundwar

Manufacturing Science-R K Jain

Thermodynamics-R Yadav Theory of Mechanics-S S Rattan

Theory of Mechanism and Mechanics-Jagdish Lal.

Mechanic of Solids-Popru

Manufacturing Science-Ghosh and Malik

Manufacturing Technology-P N Rao

Production Manangement-R K Jain

Principles of Manufacturing Material & Process-Campbeu

Other References

Subject Author
Engineering Thermodynamics PK Nag
IC Engine ML Mathur and RP Sharma
Gas Turbine and Propulsive Systems PR Khajuria & SP Dubey
Fluid Mechanics Modi & Seth RK Bansal
Compressible Flow SM Yahya
Heat and Mass Transfer JP Hollman; RC Sachdeva
Refrigeration and Air Conditioning CP Arora; Domkundwar
Fluid Machinery Jagdish Lal; RK Bansal
Theory of Machines RS Khurmi; Malik & Ghosh
Mechanical Vibration Grover
Machine Design Shigley; VB Bhandari
Material Science WD Callister; IP Singh
Production Engineering Kalpkjian Schmid; Amitabh Ghosh & AK Malik
Industrial Engineering O P Khanna; Buffa & Sarin
Operations Research Kanti Swarup
Strength of Materials Gere & Timoshenko; BC unamia; Sadhu Singh

An Exclusive Book List for Mechanical Engineering:
HUDSON, J A (2000). Engineering Rock Mechanics VOL 2
ASHBY, M. F (1998). -Engineering Materials VOL 1
ASHBY, M. F (1998). -Engineering Materials VOL 2
BAI, Y (2003). -Marine Structural Design
Belytschko T. Finite Elements for Nonlinear Continua and Structures
BIRD, J (2003). -Engineering Mathematics (4th ed.)
Bloomer-Practical Fluid Mechanics For Engineering Applications
Bonet, Wood-Nonlinear Continuum Mechanics For Finite Element Analysis
Booker J. D. Designing Capable and Reliable Products
BRANDES, E A (1992) Smithells Metals Reference Book (7th ed.)
BRANDES, E A (1998) Smithells Light Metals Handbook
Brockenbrough & Merritt-Structural Steel Designer's Handbook 3rd ed. [McGraw Hill 1999]
BRYDSON, J A (1999) Plastics Materials (7th ed.)
BURCHELL, T. D (1999). Carbon Materials for Advanced Technologies
CAHN, R. W (1996). Physical Metallurgy (4th ed.) VOL 1
CAHN, R. W (1996). Physical Metallurgy (4th ed.) VOL 2
CAHN, R. W (1996). Physical Metallurgy (4th ed.) VOL 3
CAHN, R. W (2001). The Coming of Materials Science
CAMPBELL, J (2003). Castings-The New Metallurgy of Cast Metals (2nd ed.)
CARPINTERI, A (2003). Biaxial-Multiaxial Fatigue and Fracture
CARVILL, J (1993). -Mechanical Engineer's Data Handbook
Chapman & Hall-Handbook of Thin Plate Buckling and Postbuckling
Chen, W F & Scawthorn C. Earthquake Engineering Handbook [CRC Press 2003]
Ciarlet-An Introduction to Differential Geometry with Applications to Elasticity
Cinlar, Vanderbei-Mathematical Methods of Engineering Analysis
Clough & Penzien-Dynamics of Structures-3rd Edition
CRAWFORD, R. J (1998). Plastics Engineering (3rd ed.)
CRC-El-Hawary, Ferial-Ocean Engineering Handbook [2001]
CRC-Engineering Design Reliability Handbook
CRC-Materials Science and Engineering Handbook, 3rd_1
CRC-Mechanical Engineering Handbook (1999)
CRC-Talbot D & J-Corrosion Science And Technology [1998]
CRC-The Civil Engineering Handbook
Day R. W. Geotechnical Earthquake Engineering Handbook
Elsevier-Advances in the bonded composite Repair of Metallic Aircraft Structure-VOL 1
Elsevier-Advances in the bonded composite Repair of Metallic Aircraft Structure-VOL 2
EYRES, D. J (2001). Ship Construction (5th ed.)
Flaherty J. E. Finite element analysis
Gavronsky W. K. Advanced Structural Dynamics and Active Control of Structures [Springer, 2004]
Hand, Finch-Analytical mechanics
Heinbockel-Introduction to Tensors and Continuum Mechanics
HOUGHTON, E L (2002) Aerodynamics for Engineering Students (5th ed.)
HUDSON, J A (2000) Engineering Rock Mechanics VOL 1
Hunter P. Finite Element Method-Boundary Element Method
Introduction to Finite Element Method
John Wiley & Sons-Foundations of risk analysis
JONES, D. R H (2001) Failure Analysis Case Studies II
Lai, Rubin, Krempl-Introduction to Continuum Mechanics 3rd ed
Lawrence A. Soltis-Wood handbook, Chapter 8, Structural Analysis Equations [Forest Products Laboratory 1999]
Lewis, Nithiarasu, Seetharamu-Fundamentals Of The Finite Element Method For Heat And Fluid Flow