I think the answer is very simple, big rewards
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
that's all.
When you bump your faucets prize ratio, people will do all the promotion for you.
Referral commission + good rewards and you wont be able to catchup on growing traffic.
Promo time have to be like a month or so for good and strong user base.
Anti bot systems is a must. I see that your doge faucet for example, pays 1,2...5 doge per claim, doge is cheap now, make an experiment with this site, triple the rewards and observe the magic
![Grin](https://bitcointalk.org/Smileys/default/grin.gif)
Really its all you can and should do, dont bother with boring ad campaigns or traffic boosters.
Give big and they will come.