Hey,

         I'll tell you the technique that helps me.

First make sure that your concepts are clear. You don't have to spend time mugging up all the things. Just write the important points and formulae on a piece of paper. Now, open some good book and start solving the sums from the beginning----start with the easy ones, first. And all the while keep the piece of paper containing all the information open, in front of you to see the things you require to solve any particulsr sum. You will find that after doing about 20 to 25 sums you can remember all the formulae correctly. Once you have done this, then just keep on practising and doing as many problems as you can.And after a few days you will find yourself to be the master of complex numbers.

           

If you find this helpful, please do rate me.