Depending on what ingredients you use, you may find it tricky to get a frothy head on your cocktail. However, if you are desperate for a bit of foam, you have two options. The most common way to add froth to cocktails is to add some egg white. While this may seem a little strange if you've not tried it before, it is the easiest way to build texture without altering the flavour. One egg white will work for around 2-3 cocktails.
An alternative method is to add some pineapple juice to your drink. If shaken vigorously enough pineapple juice will froth up, allowing you to pour a foamier drink.