As I've been told it is against Google's Terms of service to say, please click on an ad. Is there any way to promote the ads that is in line with Adsense's Terms of service AND ethical?
You could say "please support our sponsors" and then argue that Google doesn't sponsor you page or site. But I really don't think there is any need to encourage people. Pretty well everyone know what these ads are and that they are an invitation to click through. If they are interested they will click on them.
I was thinking of "Hey, you like what I have to offer? If so please pay attention to my ad box?". The intention isn't to guilt them into clicking. It is to get them to look at the ad box and they can decide for themselves if they want to click in it. If this is against Google's terms I would rather keep my Adsense lower than risking having them yank it all together. I'm not trying to deceive... just encourage. As I see it, it is no different than using flashy changing colors. However what I'm afraid of is Google not seeing it the same way.
I would say that would be asking for people to click. Ultimately Google is the judge though... if you think it might be a violation, simply email them, they are good about getting back quickly.
"Incentives Web pages may not include incentives of any kind for users to click on ads. This includes encouraging users to click on the ads or to visit the advertisers' sites as well as labeling the ads with text other than "sponsored links" or "advertisements." I'd be pretty willing to bet that anything other than the two things mentioned above would probably be something google wouldn't be too happy with.
I would suggest avoiding talking about it. I found people will click on them. Just worry about driving traffic to your site, and keeping people interested while they are there. If they're there long enough, they'll notice the ads. Once you get a lot of traffic, keep in mind that Google offers channels. Try placing the ads in different locations on different pages and use the channels to discover what gets people to click on the ads.