Hi Sanket
Writing Assembly code for IA is complex –but a lot of fun and very, very educating. You learn a lot about the architecture.
Here is a recommended reading for you. It explains things like Pre-boot Sequence, IA operation modes ( real mode, protected mode, SMM), early initialization, Memory Configuration and Initialization aso.
Booting an Intel Architecture System, Part I: Early Initialization
http://www.drdobbs.com/parallel/booting-an-intel-architecture-system-par/232300699
Booting an Intel Architecture System, Part II: Advanced Initialization
http://www.drdobbs.com/architecture-and-design/booting-an-intel-architecture-system-par/232400476
Some years ago a friend of mine published a document that is a good read as well:
Minimal Intel Architecture Boot Loader - Bare Bones Functionality Required for Booting an Intel Architecture Platform