First of all one must know why to do MTech. Most of the people do it to learn better things to do in life and to get a better job. For this one must join good institutes like IISc, IITs, top NITs, BITS other select places like TIFR, ISI, CMI and good IIITs. Now if you join any lower place, you are basically wasting 2 years -- this is more valuable than say fee at IIITH. Now if you're considering only such worthful places GATE is the primary exam for selection. Most of the places give direct admission based on GATE score. IITD, IITK and few seats at IITH have interviews. Only other exams worthwhile are BITS HD for admission to BITS, PGEE for IIITH and TIFR for direct PhD admission to TIFR.
If you are considering MTech research or equivalently MS then they also shortlist on the basis of NET or other national level tests. You can get the full information here-
http://gatecselastrank.com
