There are two ways to stow a shoulder-length runner. The first way is to simply sling it over your shoulder; and the second is to "triple-it" or turn it into a an alpine quickdraw.
If you prefer to keep runners slung over your shoulder, you should keep them oriented the same direction so that they don't get tangled. You should also consider leaving one carabiner on each runner. If they are pre-rigged with carabiners, then it is easy to simply clip the other end directly into a cam. Cams should also all be racked with their own carabiners to make this a quick and simple operation.
I usually carry some of my slings over my shoulder and others on my harness. Those on my harness are set-up as alpine quickdraws so that I can easily extend them.
Michael Silitch worked as an AAI guide for many years in the Cascades and Alaska Range and now guides for the Institute part time in the French and Swiss Alps. He has put together a nice, short video on how to make an alpine quickdraw. Check it out below:
Some climbing skills -- such as rope tricks and knots -- are best practiced on the ground. I like to refer to these skills as "TV watching skills." In other words, these are things you should practice while zoning out in front of the boob tube so that you have them completely dialed. The alpine quickdraw is just such a skill. Get it wired when it's not critical and it will be easy to make or open up when you are in cruxy situation on the sharp end of the rope...
--Jason D. Martin