The Great South Run Pre-Plan
Most training plans are 12 weeks long and this is sufficient to achieve success. The key to succeeding in any distance over 10k is endurance and making sure you have a good solid foundation on which to build up your mileage. Ideally you need to hold a base mileage for at least a month prior to starting the 12 week programe (starts w/c 31st August). This base mileage isn't set in stone but again ideally between 6-8 miles per week if you are fairly new to running, and 10-15 miles per week if you are more experienced. The idea is that you run at least twice a week and that you increase your mileage and long runs by about 10% each week. You want to make sure that you reach the start of the program with enough endurance, strength and without injury.
So if you are running once a week at the moment, think about the next 10 weeks or so, are there any 10k races that you could enter that would give you some experience (there are some nice ones coming up in May, June and July). Can you get out once more on a weekend? A parkrun or meet up with a friend for another 5km to add to your week. Then slowly increase your longer weekend run by a mile if you can each week to a maxium of 6 miles (I know that seems scary but don't panic).
If you are more experienced and have completed a couple of 10k's then aim for your base mileage to be about 15 miles per week, again build this up slowly and add a few 10k races in between now and the end of August. Your longest run, if experienced should be about 8 miles maximum, but talk to me if you are unsure.
Remember, by the end of July you should be working towards your base mileage so that you can sustain this for a month, again don't stress too much as holidays do get in the way. I will be producing a number of training plans for different abilities so there will be one that fits you, I will also be organising runs at the weekend to help with training, the main thing is not to panic, we really do have a lot of time, you just need to start planning and thinking how you can fit the extra run/runs into your week.