I'm trying to beat my previous timing in running, I am wondering if there are other runners out there that know a thing or two that I don't?

I'm able to run 4 miles in 28 minutes but that's without me being in tip top shape. Average is 30 minutes.

I can run 13-14 miles no problem within 1:50hr, I have done 100 minutes 37 seconds for 12.9 miles.

I have been smoking since June 19, 2010. I'm planning on quitting smoking in August and getting back to working out. I haven't run for a week. When I get back into running, I really want to beat the 25 minute mark for 4 miles.

I eat eggs for breakfast or I alternate between bread cheese and an oatmeal. What are some things I can do to improve my timing? I already said I'm quitting smoking in August.
I'm trying to beat my previous timing in running, I am wondering if there are other runners out there that know a thing or two that I don't?
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