Back on topic now 🙂
I find word of mouth is the best, 90% of my customers have come from word of mouth, they tend to be prepared to pay for deliverable packages rather than expecting you to compete with thr 5Gb for $1 type offers and from my expereince they will ask less support questions and stay with you rather than jumping ship when the next offer comes along.
Your current customers are your best advert 🙂