I know this is obvious but it is also important to remember: exercise should be pleasant and relaxing.
If you live by a or work by a park, please, get out in it and walk and run and play frisbee or kick a ball about, parks are interesting, ever changing and you even get to see the sun once in a while (very important in northern latitudes).
I have been walking about Clissold Park, our local park, a lot recently and it is lovely in the Autumn. I used to work right by Regents Park in London and I kick myself that I didn’t follow the example of my work mate Neil and take a daily lunch time stroll.
Walking around a park never feels like exercise, running on a treadmill always does.