I have this quite often and love it because it is refreshing and different.

Either in a pot boil 5, 3cm cut pices of washed lemon grass leaves, cover with about 500mls of water and boil. Once boiling turn off and let it cool. Either drink warm or cool and refridgerate and have as a cold drink.
In a coffee plunger put about five 3cm cut pieces of washed lemon grass leaves. Poor hot water over and let it rest. Drink when cool enough. You can add some honey or ginger for another twist in flavour.

It is great as a cold drink by itself or you could add other flavours, fruit to make it better for a hot day. Flavouring can be changed and improved, its up to your imagination.

I grow my own lemon grass and it is easy to care for and great to use.