aim for
1. To point or guide an object, such as a weapon, at a target. Make sure you aim for the target before you pull the trigger. His water balloon is aimed for you! Run!
2. To strive to accomplish a particular goal. After studying all weekend, Amanda is aiming for a perfect score on her history exam.
aim for something
and aim at somethingto strive toward a particular goal; to direct oneself or one's energies toward something. You should aim for success. Aim at getting this done on time.