Do you sift the flour before you measure it or after?

When baking, optimally the ingredients are measured by weight, not volume. However, most recipes still call for volume measurement. The general method for measuring flour and other loose dry goods is spoon then scrape to level the cup. If the recipe says 'x cups flour, sifted', then sift after measuring.

This is why I prefer weighing ingredients - no confusion!

It depends how it's worded. In this case, you sift and then measure. If it said one cup flour, sifted, it would mean measure and then sift.