what i do is just aim for say a 5min run and then build up, but dont stop keep moving until you have done half hour workout. run walk run walk. three times a week. on a nice oval. you will get to half hour and then try hills, when you can do hills, race ... race improve your PB quickly, here in townsville (i know its a bit out of the way for a weekend race) we have a race a varying distance every week --- it is a great way to improve fitness (my aim is just to beat a friend of mine --- she is 15 years older than me and has 3 kids ..... each week we have a bet (coffee post race) i was only shouted 5 times last year but this year shes mine
also i have a smallish 3.5km loop around the uni that is perfect to race PBs, so I would recommend getting your own little track where you can try different techniques to determine what works best for you
and keep at it, and try not to get discouraged with poor performances, we all have them.
