I don't know exactly how it relates to the broader "tech debt" discussion, but one thing that can make a big difference is to design systems in such a way that there are obvious strain indicators.
To quote Firefly, ways the system can "let you know she's hurting before she keels.".
How exactly you do that depends on what you're building, but I think it's a worthwhile thing to keep in mind.
Can't think of any specific example off the top of my head, but I've noticed that lots of places talk about needing people to be "on call" all the time. We are a very small shop with some fairly high profile clients, and "everything's on fire" situations happen maybe once every year or two. And are then mitigated by fixing the code in such a way that there are diagnostics to let us know if we're ending up in dangerous territory again. Before everything goes Kaboom.