Greetings Amit

Congrats on completing 12 one more step and you can land into any college offering B tech. 

For getting admission into btech you need to answer a entrance test after 12 std in science. In entrance test you need to get good rank. 

Their are several  types of entrance test in India they can be broadly divided into 3 types 

1. National level

This includes exam like JEE Advanced ,  AIEEE.  By clearing this exam you can land into IIT or NIT

2. State level exam 

This exam is conducted by state and only the residents of that state are eligible to answer that exam. For ex in Goa it is CET likewise depending on state the entrance exam is different

3. Private University exam

The private university conducts their own separate exam.  And the seat allotment is done based on the rank obtained in their exam. 

For ex Manipal Institute of Technology conducts exam called as MUOET every year for Btech