If you're the type of person who loves to read, you can go to:
http://www.empowernetwork.com/stephansteve87/blog/how-to-sell-stuff-on-ebay-never-trade-in-your-phone-at-low-prices-again-cash-out-on-items-you-dont-need-whenever-you-want-to/?id=stephansteve87
If you are still selling your stuff to 2nd hand shops at low prices you are missing out. Ebay is a great way of selling the items that you don't want! With it's bidding system you can sell your items at a higher than your minimum price (usually). Here @stephansteve87 does a walk through of how exactly to do it.