A key to project success is eliminating risk. We've all seen that cartoon with the big chart on the board, and in the middle is a box labeled ThenaMiracleOccurs.
An ExtremeProgramming team identifies tasks by risk, and works to assess and eliminate risk at the beginning (WorstThingsFirst).
Turn the big thing you don't know how to do into smaller things you do know how to do. Try a SpikeSolution. (see also SpikeDescribed.)
As soon as the task isn't the biggest risk, capture what you have learned and turn to whatever is now the biggest risk. --RonJeffries
Eliminating risk may mean buying the program or the knowledge. A project I'm in touch with has spent the last N months inventing concurrency and persistence. It hasn't done anything about the application. They are in serious danger of getting pulled up by the roots.
Identify the right risks; reduce them quickly; get on with it. --RonJeffries
Someone recently told me the real risk probably isn't a TechnicalRisk, but a PeopleRisk?. Its the things you think you know about people that ain't so. ExtremeProgramming and SpikeSolution won't necessarily help you with this. A lot of watching out of the corner of you eye will. --AlistairCockburn
Oh yes. That's kind of my job on C3 ... I just mill around watching for things going wrong. Over the course of the project we've helped a number of people improve, and helped a couple leave. --RonJeffries
Note that actually YouCantEliminateRisk.