Read Divatologist's blog, she has written terrific manual on this subject.
Still, I am witnessing the fact that old time brands that had to be applied with caution are way weaker - to the point that local cheapos (ie, Avon's! Yes, Blue Suede made in Argentina has more longevity and sillage than Azzaro pH made in France) are better in terms of longevity and sillage.
Blame it on IFRA's guidelines, cost efficiency politics impacting formulation, price increase in key raw materials or plain greediness - I imagine managers saying something like "let's make fragrances weaker so customers have to increase purchase frequency" - but the fact is that many of the old brands that used to be "bombs", like Antaeus, Azzaro pH, or subdued, like Equipage and others, don't last the way they used to. I regret this, really.