The tip I once received from Danie Bles and that I still apply: use an eyebrow gel. And when you go for the gel, take the one from Maybelline.

With the small brush, you give yourself a free eye lift, because the drooping eyebrow is pulled down just that little bit extra by gravity. You brush the hairs exactly the way you want, up, to the side, and not down. And it gives the transparent strays just a bit more color. Brown for the brunettes, dark blonde for myself. We buy them in bulk, because the entire editorial team is addicted to Maybelline's eyebrow gel. By the way, it's a bargain, because for ten euros your eyebrows look a-breath-taking.