The correct way to increase distance

Hi, I'm a fitness freak, but still very much a newbie as far as running is concerned. I haven't followed any training plans, but just started running over the last few weeks.

I pushed myself today and managed five miles in just over forty minutes. Previously I had been running for just twenty minutes. I don't feel tired or breathless now, but do get some mild pain in my legs. 

Is there a standard approach when it comes to increasing distance, or am I doing too much too soon? I'm really in love with this whole running thing, so don't want to do any damage 

Hi James, you say your a fitness freak so guess your just new to running and do other sports regularly? I'm a newbie too and the majority of people seems to be saying up your distance by a MAX of 10% per week and some say add a mile to your weekly long run each week. I've just started my LSR's again and starting at 10k will be adding 2k per week for a month then dropping down a week before (maybe) increasing again.

Thanks guys, that's really helpful 

I found the 10% thing difficult to keep on doing without taking a rest week where I'll run between 50-70% of my highest weekly mileage every three-or-four weeks.

But over the past six weeks I've changed that and I've built upto 22 miles now for my long weekend run (I like running long and slow though I do try to put some speed in during the week too), and found that increasing my mileage by 1 or 2 miles every-other-week, with a shorter long run on the weekend inbetween easier for my body to handle.

It just gives my niggles time to recover before they turn into injuries I think.