Hey there man, basically my main piece of advice to you is you can't be lazy. The most important part of a run cycle is you take your time and plan carefully how the character will move. Dont forget that the whole characters body will move, not just his legs. This is important to make the run cycle look more natural. Also when you start drawing start with the main stages of a walk. The points at which each leg are highest from the ground and then work your way though adding more frames, making the motion more smooth.