What I do is just go out one day and run as long as I can. I think people assume they should just run 30min everyday for a few weeks then add slowly. I just go out and do a long run after a few days of easy 20-30min. Lets say I have been running about 30min average, I will go out and do an hour long run. Then I will bump that long run to an hour 15 or 20. Then 90min to 2 hours. Trust me this really helps and I get back into shape very quickly doing this. To me this is how I interrepted what Lydiard said about varying the distances everyday and he emphasizes the longer runs. Just go out as soon as you can and try to run double the longest you have run but go easy/steady. I usually just go out and after 30 mins I check how I feel. Like 35min I will decide whether I can keep going or not. Then I tell myself to try to make it to 35min, then 40, and so on. Trust me you will get back your form, mostly because this helps break that mentallity that your out of shape and lost your form.
Good luck