How you split them up depends on how many days per week you want to run. I cheat a little, I space my races out so I'm ony a few weeks between training for a specific event but on my "non-training plan" weeks I tend to stick with fairly easy runs (ie not worried too much about pace or speed work) and will typically go short & easy on Tuesday (5 to 8 km), 10km easy on Thursday, 5km on Saturday and then (depending on my mood) 10-16km slow on Sunday.

That sounds great. Your Mon and Wed can be speed work and hard hills with the Tues easy. Make your hard days hard and your easy days easy...if you're weight training do it on hard run days. Try not to put hard workout days next to eachother. You have 4 basic runs... tempo -speed -hills -long run. You can make a 10-14 day rotation, it doesnt have to be 7. I get Runners World, Running Times and a Ton of the Runners World books and they all say pretty much the same. If you dont want to run a long run that weekend..don't. If you want to make a longer run shorter or a shorter one longer ok... keep a log!! Runners world has a great one they sell...i buy one every year. AND i have one my daughter made me. I keep one by the treadmill and one by the front door. If you aren't training for a race then anything goes as long as you are running at least a couple times a week to keep cardio fitness.