If you have a client who hasn't yet got a website, but it's in development and they have hired you to handle their SEO, what goals should you set for those first 3 months? You can't say 'Increase traffic by 200%', or 'Increase conversion rates by X' as there is no previous data to work from. Should I look at the keywords and look at potential traffic and use that as a guide?

My primary question is what is stated in the title, 'What should SEO goals be for a completely new website?'