I have an Abus chain lock to secure my Bianchi.
So far I've been wearing it across my upper body, it seems like the fastest and most easy way to carry it along. Problem is, the protective fabric on the chain lock has gotten more and more dirty with oil from the chain on the bike and that doesn't go well with a white shirt, I'd rather avoid those black stains on my $150 shirts.
Alternatively one could wrap the chain lock around either the saddle post or the top bar of the frame but I find it annoying as my legs occasionally touch it while riding and it rattles like crazy on bumpy roads. It's also annoyingly time consuming twisting and untwisting the chain lock every time you have to park your bike.
A backpack could also be the option but that's even more troublesome and I'd have to carry a backpack for no other reason.
How do you carry a chain lock around or how do you avoid dirty stains on your clothes from it?