I found the best way to get back into exercise is by doing things you enjoy doing.

I started by cycling by the sea and running along by the river - it was just a case of not thinking about it, putting on my gear and getting out the door. And because I like doing those after a couple of weeks it was easy to throw in things I didnt like such as press ups and abs...

And like Nova said, food and diet will change you energy levels dramatically - don't forget water