the important thing is to present the answers on tax in a logical manner...first state the problem, then state the relevant section and any relevant case laws and then conclude on the position.. (this shall apply to bigger questions)
for questions with 1/2 marks, relevant section or case law can be referred to and conclusion be given, all in 3-4 lines
for computation, it is important that you present in a tabulated manner, clearly marking different incomes heads, then sets-offs, chapter VI, and thereafter computation of tax liability. Assumptions should be clearly stated. Positions based on case laws should be clearly explained.
Wherever possible the main computation should only reflect the final taxable income under each head and set offs, chapter VI and net tax liability (including rebates on tax like 87A). The computation for each head should be put in separate notes.
the problem with the above is that you wont be able to complete the whole paper if you answer in the above manner unless you practice a lot before the exams.