Just as they sound, fingertip push-ups entail doing push-ups by only holding yourself up by your fingertips. These should be military push-ups, where you place your toes on the ground behind straight legs and then your hands on each side of you under your shoulders. You should then try and lift yourself up on your fingertips on each hand and try to do a push up. This will be difficult at first, as your hands and fingers will not be used to it. Don't force yourself to do it, as the last thing you want to do it hurt or break a finger by putting too much weight on your hands. Try to do one or two to start, and then gradually work up to five or ten in a row. All the weight and pressure will make the muscles around your fingers and fingertips much more solid, so you can grip and football better and rip it out of a defensive back's intercepting grasp.
All you will need for this drill is a football that is the same size as the one you will use in the game. Hold the football in one hand solidly and then gently flip it up so that you can balance it on the back of your hand. Balance it for a second and then flip it back around so you can catch the ball again with the same hand. While this may just seem like something that is a fun trick for bored receivers, it is actually one of the best things you can do to improve your hand eye coordination. Try to do this every day with each hand, as it will train each hand to be as good at catching a football as the other. It will also train your hands for the size and grip that will be needed to hold a football.
This is a drill used in basketball among players to help improve ball handling skills but this is also good for receivers when improving their hands and dealing with the momentum of a pass that they are trying to catch. Spread your feet shoulder length apart, cradle the football in one hand and bend over slightly. Then move the football through your legs in a figure 8 pattern, circling each leg and handing the ball off in the middle. This drill will also improve hand eye coordination and is something you can do on your own a couple times a day, to really improve your receiving skills.