The followings factors are involved in improving or optimizing your existing PPC campaign:
Keyword Optimization
Landing Page Optimization
Text Optimization
Bid Optimization
Quality Score

Begin with keywords that actually drive conversions and also perform some additional research on other keywords which are missing. That will actually make the initial list.Once you start running ads on that list, you can get a improved idea of whether they are going to perform.You can also notably figure out what negatives need to be run, and which keywords need to be split into key phrases for better bidding.If some keywords are returning negatively then delete them.But in case they drove any conversions at all,check to see if a further precise phrase may achieve positive results for you.

Ensure that you have a fine landing page that enables people to obtain the information they are seeking.

Next optimize the advertisement text. Remember that PPC campaign involves conversions. Suppose your campaign deals with real estate, ensure that the word exists in your ad text,so that people who are uninterested in that topic need not click the ads.

Be wise enough not to bid for the top most place.Try to bid for a bit lower position especially if your budget is tight.

Finally, test all of your quality scores(QS). Fix any trouble Google points out as they prefer ads that possess high QS.

Check the forum which gives sufficient information regarding PPC campaign forums.seochat.com/google-adwords-more-39/optimising-keywords-advice-256137.html