So my family and I are trying to get in shape this summer.
Running and Swimming are the fastest ways to get in shape, lose weight, feel better, anything but strictly build muscle. Swimming is all around better but you need access to a pool if you want to do laps.
If you want to go for a run running as long as you can or as fast as you can isn't necessarily the best way to do it. You build more muscle if you stop frequently and if you walk for five minutes then run for five minutes that's good for cardio training.
You also have to run right. Stand up straight, don't move your body too much or twist it, run on the balls of your feet and not your toes (your heels are better for absorbing shock so you don't end up getting crummy knees) and so on. It sounds like a lot but once you start doing it really does feel natural and better (because it is better).
Strength training is important too, but I really hate it so I just don't bother. Strength training sounds like something you only bother with if you want a six pack but it isn't. It's a good idea for anybody to do it. I don't do it but I'm not a model of fitness.
My mom is a personal trainer and while I don't know everything she knows I can probably answer any questions you have. Even if it involves strength training, I've had to do it plenty of times.