When to get the Epidural?

Getting closer to due date so I'm planning ahead. I had the epidural last time but I believe I got it so late because it had no effect on me what so ever, I was in so much pain!! the advantage of this was that I knew when to push so I had my daughter out in 2 pushes. 
I still want the epidural however, I don't want to be in pain and still get it in time but also still want to know when to push. When is the best time to get the epidural.???
I'm open for you to Share your experiences or opinions? 
(This is my second child)