About how many days should you run a pay per click ad test to know if your campaign is working or not?

[Jason]

Rather than thinking in terms of days, I would suggest you think in terms of impressions and clicks. 1000 clicks is usually enough to form a solid opinion on a particular landing page, but if you're test budget isn't big enough for 1,000 test clicks, then 300 clicks would be my minimum.

Of course, 300 clicks for one specific landing page and one specific ad would be best. When you start to include multiple ads, it's harder to make a judgment about what's working and what isn't.

The same goes for Facebook really, but I would suggest focusing on AdWords first. The ROI is usually very good on AdWords, but I've had only minimal success with FB.