Regarding the above few posts, the recommended way of making sure your hands are in the right place, is to start your push ups lying on the floor (rather then get in to position then go down-up-down etc) and simply place your hands underneath your shoulders and then push up, and DO NOT move your hands to a more comfortable position (so you'll be starting your push ups going up-down-up).
As stated, hands should be slightly closer than normal push ups, so get practising using this method, as it places more strain on the triceps than the chest compared to general push ups.