i would recommend doing research on <b>call to action</b> phrases - like, "get," "learn," "buy," etc. there is a lot of material out there that will give you an idea of what someone may be more likely to click on. however, it must be very tightly related to what is on your landing page. you can advertise "free" whatever and if your landing page is not tightly related to the ad, you can get a click through rate of 5% and not have one single conversion. put the keyword in the title (and in the copy if possible), put the offer in Line 1, and the customer benefit in Line 2. good luck.