Step One: Paint nails in the colour of your choice, I like feathers over natural nails so I used Rimmel Lycra Pro in French Manicure. (I used boots 'save the nail' 'eau so hydrating' base coat and '45 second topcoat'.)
Step Two: Get a feather ready for your nail, I took a marabou feather and took some of the little feathers from the base. It's easiest to use a feather longer than your nail so you can hold onto the bottom and/or top when applying.
Step Three: Paint a topcoat over your nails and place the feather carefully on top. Don't rush, it helps if the topcoat dries a little so when you place the feather on you can gently pat it down till it sticks.
Step Four: Snip off the excess feather, to trim the bottom use the scissors perpendicular to your finger but be really careful, feathers are thin so you don't need a lot of force to cut them and you don't want to cut yourself!
Step Five: Paint another topcoat (or two) over your nail (you might need to trim the feather again if you drag it up a little).
And you're done! It's actually pretty simple and really effective, I decided to do them for my black swan costume for Halloween. Don't be scared to mess up your nails, if you put on a feather a little wonky just peel it off, paint another topcoat over and use another feather.