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Android uses RAM differently from a PC. Full RAM is a good thing. Apps load quicker, and the OS doesn't waste energy bringing up data it needs. Now, there is a difference between full RAM and you utilizing all of your RAM for what you want.
I would go into Settings>Application Manager and swipe over to all apps.
Anything that is bloatware, say Yahoo News. Click on it. You will see the Application Information screen. You will see two buttons; Force Stop and Disable/Uninstall Updates. (Uninstall Updates needs to be clicked first in order to disable). Disabling any app that you have no use for will free up more RAM for your use.
For future reference, there is a check box below those two buttons, 'Show Notifications'. Unchecking this box will disable notifications from, for example Yahoo News, from going to your notification bar.
Download Android System Info from the playstore, it 'll show you every single tasks running default in the background and how much ram and CPU they use.