There are number of entrance examinations conducted for M.Tech.
Some of them conducted on national/all India level while some on state level.
You can also take M.Tech course after taking degree of B.Tech from same college.
You can get more information regarding this site: ” http://www.mapsofindia.com/education/career/m-tech.html”
This site contain information about different entrance exam along with its link.
All the best