Admission for NSIT, DTU and IIITD will all be based on JEE main score and the admission process will be carried out by JAC Delhi.

For NIT, the admission is based on JEE main score, and the procedure is carried out by JoSAA.

For these two, the process will start from the last week of June for both the JAC and JoSSA.

For GGSIPU, the admission is based on their admission test. The admission will start from last week of June.

The following links will help you out:

https://engineering.careers360.com/articles/ipu-cet

https://engineering.careers360.com/articles/jac-delhi-application-form