Good article Palak . But I w'd like to add more to it.
@ O/H- May be it doesn't contain much weightage but it is a very imp. chapter. To have command over costing a complete knowledge of O/H is necessary.
@ Basic Concepts-- You can refer compiler for it. No need to waste time on it.
@ Reconciliation & Integrated A/c's -- well not much imp. chapters but institute can surprise you by asking 8 marks numerical q's from it.
@ Standard, Marginal & Budgetary -- Comprises 20-25 marks paper and I mark it as Institute's Fav.
@ Contract , Process & Operating Costing -- Requires good practice and is very imp. from exam point of view and not much difficult.
@ Material,Labour & O/H-- Basic chapters of Costing.
Best Tip -- To score good marks in Cost + Fm focus more on FM as it is more scoring with less course.