Going to give HIIT a go
This is teh gay, but I've found it very effective. Start slow, stay with it, and you'll work up:
http://bodyforlife.com/library/exercise/cardioBasically it's 20 min - you warm up for 2, then do four cycles of one min each, increasing the intensity. Then, each subsequent workout, you beat the previous. A start may look like this:
Each increment on the left is one min
1 - 3 mph walk
2 - 3 mph walk
3 - 4 mph
4 - 5 mph
5 - 6 mph
6 - 7 mph
Repeat for minutes 7-10, and 11-14, dropping to 4 mph then working back to 7
Then:
15 - 4 mph
16 - 5 mph
17 - 6 mph
18 - 7 mph
19 - 8 mph
20 - 4 mph
Fin.
Next time, minimum can be 4.1.......increase the intensity withing the 20 min.
I'm not sure if the science is correct, but I've always started this way after a layoff and it's worked. Now I can get to 7 mph minimum, and do a sprint circuit after the 20 min when I'm done......
I tried a 5k after zero running last year and it took me 33 min with 10 stops. Pathetic. Did the exact workout above on a treadmill for thee weeks after, then tried the 5k again and did it in 24-25 minutes easy. So I'm a believer in Mr. Bill Phillips' plan.