What most people do is choose as many keywords as they can and later realized they are loosing much money on PPC campaigns. Keyword relevancy is the main concern. In PPC, every click is valuable so targeting the right person is important.
What you need to do inorder to have greater success is to determine the relevancy of your keywords. Google is pretty particular now about adword relevancy, so my advise is, pick one. How to boost adwords relevancy? Select one keyword and one adgroup and use exact match. If you do this, your relevancy score on Google will increase, and that’s the goal. Don’t waste your money on 20 or 30 keywords when one can be more effective.
When you have selected your keyword, be sure to use exact match. Then make sure you put that one keyword in your URL, your headline, your description, etc. Make sure the keyword density is high, and you will see greater success.