Proper Meditation.

I have been trying to meditate lately, but im not really sure what to expect. I dont understand what it means to clear my mind of all things, since im usually thinking about everything. I try to blank everything, but soon thereafter thoughts enter my mind, and i feel like a failure. Is there anything I can read to understand how im supposed to this. Im hoping to heal spiritually, and develop better cognitive skills. How will I know when i have had a successful meditation session? Thanks!