Explicit "I told you so" is a bad idea, but I've found that you can often guide people to it with other questions. For example: "How might this have been avo

Explicit "I told you so" is a bad idea, but I've found that you can often guide people to it with other questions. For example: "How might this have been avoided?" "What lessons can we learn from this?" "What else could we have done instead?" As the answers to these are explored, some people might realize that the approach or principle you had earlier espoused was worth keeping in mind next time. They might even associate that idea with you, but that's not really important. The important thing is that the next time people are about to same mistake (which almost always happens), your objection will have the weight of shared experience and analysis behind it. BTW, this is an example of a general approach I've found useful. If you can lead people to the realization that their original solution is not the best one, they'll view you as a collaborator rather than a competitor. Emotional reactions matter. Too few will ever admit that their original idea was wrong or that the better idea was yours, but they might well realize it themselves. Over time and repetition, they'll become more likely to listen. It's kind of a shame that this extra work is so often necessary to overcome others' ego, but ... well, it is.