I've looked at several tutorials on how to get the perfect neat french tips and found this method works best for me.
Step 1- Apply a layer of white polish to the top of your nails, this does not have to be perfect (I used OPI- Alpine Snow)
Step 2- Dip a small brush into some nail polish remover or acetone and begin to remove excess white polish from nail, creating a neat line.
Step 3- Once nail polish is dry, Apply two layers of top coat (I used Essence Gel Look Top Coat)
Optionally you can apply a light pink colour over the white before layering on your Top Coat, in order to tone down the bright White and make it a more natural colour.
Here's the results!