dear sangeeta
Though i dont know particular question pattern of HAL. In general the question pattern of All Public Sector industries will be like this.
50% English, Quant, reasoning- Concentrate more to score in this paper.
50% Humna resource management.
Concentrate on OB and HR part compared to Labor Laws as most of these organizations give questions from OB and core HR and principles of Mangement in written test.
Sugested books are: Stephen robinson _ OB
Principles of managemnt : Koontz & weirich
HR: Any HR book like Mamoria, Subba rao, Stephen Robinson which gives basic back ground.
Books like 300 Models in HR by Kandula srinivas rao and other books which give you insight in HRD interventions.
Labor Laws: Khan and Khan
these books will assure sucess in written test.
for Interview concentrate more on Labor Laws. You read KHan and Khan by Asia Law pulications. Don not miss it.
In general written will be given 80% weightage and oral will be 20%.
I have cracked all the Navratna PSU examination through these Books.
regards
ravi