geesh, does it have to be so "in your face"? a dried pot leave to sybolize you gave up pot? why? you can pick any design you like and to you it means something.
Why not tattoo "I gave up pot and smoking!" across your collar bones.
What if, you decide to pick up smoking again later in life? wouldn't you look like a total douche-fag with a non smoking tattoo?
No offence.
[/rant]

What kind of tattoos do you like?
Do you have any other tattoos?
Where do you want it?

and why can't you think of anything? If you come here for advice about what to get, imo you shouldn't get a tattoo just yet.
Find something you really like, and sit on the idea for a couple of months. Talk to a tattoo artist about whats possible, and take it from there.

no harm intended.