As I explained previously I tend to complete an Iteration 0 prior to the rest of the development team starting work on a project as I feel it helps ensure that the development team can be as productive as possible when they start. Normally I spend this time coding alone, but consulting with others as required, putting the structure of the system in place. I make decisions about the main structural patterns we're going to use (e.g., Domain Model, Service Layer etc.) and the technologies (e.g., NUnit, NHibernate, Spring.NET etc) but I try to defer as many as I reasonably can. If I don't spend this time I've found that Iteration 1 is spent arguing about the best way to do just about everything and frankly when you're working on fixed price contract you just can't afford that.
Once Iteration 0 is complete and the rest of the development team start they concentrate on cranking out functionality as quickly as they can. They don't really need to know about the dependency injection framework, the fancy AOP aspects intercepted to provided comprehensive logging to all the services exposed. The project naturally gathers pace and for most of the developers the plumbing code is a bit like magic: it just works! They don't know how and, to be honest, they don't need to. It's at this point when the warning signs appear. If you're the Technical Lead and nobody on your development team is starting to ask those awkward questions that make you re-evaluate your view on things like "why is the logging like this?", "why aren't we using Fluent NHibernate", start to worry. If nobody on the development team other than you is taking the time to understand what's going on under the hood and questioning your decisions, rest assured that if you step off that project monsters will be eating your bridges in no time at all.
Now, on one of the systems I've built when I stepped off and went back later to make a bug fix, there was no sign of monsters. So the question is: what was different? The answer is that on the project one of the less experienced developers on the development team started asking awkward questions and I started answering them. Some of the questions were straightforward to answer, but some of the questions made me really question the decisions I'd made. The less experienced developed started to understand not only how things were put together but why. They started to learn, fast! When the time came for me to step off the project they were then capable to assume the role of Technical Lead and the "Sim City" effect didn't happen. Sure when I returned things had changed but there was no monsters in site.