The famous places for spotting of high speed trains are as follows :-
Phagwara / Jalandhar Cantt - Punjab
Ambala City / Jagadhri - Haryana
Baruipara / Durgapur - West Bengal
Whitefield - Karnataka
Nallasopara...
more... - Maharashtra
Palwal - Delhi Area
Vindyachal / Chunar - Uttar Pradesh
Dehri - On - Sone / Babua Road / Buxar - Bihar
Koderma / Gomoh / Simultala / Hazaribagh Road - Jharkhand
Jajpur - Keonjhar Road / Kurda Road / Balasore - Odisa
You can add more places from more states or even the states mentioned above . Thanks .