I have ford contour GL 1995 model car, when i am trying to start car it cranks but it not starting?

I have ford contour GL 1995 model car, when i am trying to start car it cranks but it not starting, after several try it started, I want to know why it is happening? any thing i need to replace to correct this issue.I have ford contour GL 1995 model car, when i am trying to start car it cranks but it not starting?try to check it out first on auto repair shop...