The first thing is to list your product or products.Then list all the keywords relating to that product or service.
It is also advisable to chose mispelled words. Example is to take or spell words like product as produks or produck.You do this to enhance your chances of having your product on the first page of google. Also your ads can get clicked on words that your competitors do not have.
It is also very likely that some of your words or ads can get clicked for very lowprices.This is important because the position of your adword ad is determined not only by the maximum click price you are ready to spend. The google first page recieves most attention because it is the most expensive page
Also the title or headline in the adword ad must catch the viewers attention. If you place the keyword in the headline more properly you will definitely get more clicks to your adword ad and better results.
Try to tell viewer why he should click on ad.Tell him what he stands to gain.Motivate him through your words to click on your ad.It is not out of place to say if your product is cheaper or what incentive or bonus you gain by purchasing the product. Avoid price wars with your competitors. Instead find search terms which has more words and are more precise.
Have precise words that have relevance to product so that search by a finder targets your product. Use excluding keywords.these are words for which your ad do not appear.This will prevent you from paying for ads which are clicked on but do not relate to what they need.
It is vey important to create for all your adword ads a landing page. Hope these tips prove useful to you