The brain disposes of any "unnecessary" information so it will be able to get new informations - the problem is that it refers to unused information as unnecessary.
Information can be remembered for longer time if you process it more:
if you only hear something and not think about it, it will be lost, but if you think about it and try to connect other informations to it, you will remember it.
Within the processing procedure, you can try to connect the new information to knowledge you already know; you can build some logical story you can relate the information to, so when you'll need that information you automatically remember that story and that will trigger your memory of that information; you can make songs about the information;
Also, if you use the information in conversations or write it down or if you can do a physical action that is connected to the information, you will remember it better.
Use the information you want to keep, that is the realization.