I would like to disagree with cricket crazy.
A googly is basically a ball that does not spin the traditional way but spins in the opposite direction.
For example, You are a leg spinner. Your stock delivery will pitch and spin away from a right handed batsman. Now if you are able to make the ball pitch and spin into the batsman it will be called a googly as the batsman is expecting it to spin away from him and thus might get wrapped on the pads or cramped for space.
A skidder is basically an arm ball bowled at a much quicker pace than your normal delivery. The batsman expects a ball that will pitch and then spin. But instead the delivery pitches and holds its line. This is again good for cramping the batsman for space when he is thinking it will spin away from him.
As far as bowling the above two deliveries goes. A skidder is very easy. Hold the ball like a fast bowler and throw it straight. Now for a googly it is very difficult to write and explain, but I am sure you can find some videos on YouTube that can help you or join a coaching institute. They will teach it to you.
