Hello Jayant!

PRMO registrations have already begun. As for NSEP and NSEC, you can receive updates from www.iapt.org. The PRMO syllabus consists of four topics: Algebra, Number Theory, Combinatorics and Geometry. The well recognised book for Mathematics Olympiad preparation is 'The Excursion in Mathematics' which I think you may find useful. Just follow the JEE syllabus to prepare for NSEC and NSEP.

All the best!!