how to approach for difficult integral in iit paper

hi' there no fix rule for approach for difficult integral as u wud know during ur practice of integrals. but there r certain fix rules , generally given in every std. txt book of integral calculus, u hav to look for the types of form ,of which u know the integral, or u can manipulate the given form accord. to ur ease then u can proceed . integral calculus is not at all tough part but a bit manipulations r required, it's just memorising the fix type then apply them conveniently. good luck