The preparation for IES starts with your engineering itself. First make sure that you have done all your courses thoroughly. If you are in the final year then start solving the previous year question papers of IES. That will be of great help. IES exam consists of a single written stage only i.e. there will not be any preliminary. the written exam will consist both objective as well as subjective stages and you have to score well in both. Joining a good coaching institute will also help, especially if you have already passed out and can devote full time to the preparation.