Adding a regiment of full body stretches.

Hey Fittit, I've been steady working out for roughly two years now and I kinda wanted to work in a regiment of full body stretches. Currently I only stretch my legs before and after runs, so I was wondering if you guys had any tips on stretching that could be useful. You know like how long should I stretch each muscle, how many days a week should I perform each stretch and specifically which muscles would be the most beneficial to stretching. Any other tips too would be much appreciated.