* If you are serious about wanting a dark long lasting design, keep the henna on for at least 6 hours or longer if you can. The longer the better. 

* The above 2 suggestions may test your patience, but they are highly effective! After sufficient time, gently pick or scrape the the henna off with the back of a butter knife or finger, DO NOT wash off unless you decide you want a lighter design or you left the paste on overnight. 

* After you remove the henna, you may gently (there's that word again) rinse the area with warm water to remove the sticky lemon/sugar, apply oil if you have it.

* Try not to use soap on the area for at least a day, this allows the henna to completely absorb into the skin.