A warm up routine should include the following elements.
It's widely accepted now that static stretching prior to exercise is of no benefit and that stretching cold will damage muscle and connective tissue.
Often you'll just pick up your guitar and start playing whenever and wherever you can, especially if you have a family. To take advantage of what you're learning here however you'll need to allow yourself some more space than that.
There is a mountain of information on this site and a real danger of overload by the time you get to here. The information in this section will help you structure the program, pick out the most relevant pieces of information for you, monitor your progress and make it all work