It may vary for all the NITs. To get EEE (electrical and electronics engineering) branch in lower NITs like  Mizoram, Nagaland, Meghalaya Etc., your score should be around 140-150 and you should score more than 220 to get EEE branch in top NITs like Trichi, Surathkal, Warangal Etc.

You should try to score more than 200 in JEE Main to get decent NIT.
you can check EEE branch cut off rank of various NITs in this article:

http://www.engineering.careers360.com/articles/nits-cutoff-for-b-tech-electrical-and-electronics-engineering

Also,check cut off rank for other branches in NITs:

http://www.engineering.careers360.com/articles/nits-cutoff-for-top-btech-branches