A three words keyword phrase that keeps 0 click in 147 show. Is it worth exist? I'm afraid that it will drop down my campaign, so I stop it now. Do you think so?
Ok. So you mean that you ad was showed 147 times in 15 days for a particular keyword, and you got 0 clicks? Yeah I think you should drop it. But maybe other more experienced users can guide you better and give better advice.
It could be that your ad isn't effective enough - try spicing it up a little to entice people to click.
What is your average position for that keyword? And like Getagrip said, you might need to fine tune your ad.
Well, we expect thing to happen too quick without troubleshooting in the initial period of campaign management. I feel you should use target right keywords ( be it two / three / four keyword phrase) with decent ad text with just one "Call to action" term landing to a keyword specific page / relevant page and monitor the campaign. Remember, all the search engines work on CPC, so who ever bids high will definitely have a fair advantage in the initial stage of live campaign. You will have to tweak your bids at least 1/3 times a day to see the effect. It is a practice, if we know our CPA and we know we achieve a respected CPA, adwords marketers go with a high budget initial so that ads are served in all the google networks and for better explore. And once you have definite indication reduce the budget with quality across all parameter, adtext, keywords, landing page etc.