The amount of time you spend researching and choosing your keywords is directly relevant to the success of your campaign. Choosing keywords that are too popular will mean that you spend more money bidding for top search engine positions; making your keywords too specialised reduces the likelihood that anyone will be searching for those terms.

Start by looking in your web log to see what keywords are bringing searchers to your site at the moment. Collect the ones that appear regularly, and check their popularity in one of the many keyword search programs available. This will show you how frequently they are used as search terms, and you can decide to keep them or refine them as necessary for your PPC project. If your site is not yet up and running, you will need to sit down and brainstorm about your products and your customers to produce a list of possible keywords. Make sure that these are words or phrases that your potential customers are actually likely to use when using a search engine; "get" is more liable to be used than "receive" and "buy" more likely than "purchase".

Make your keywords specific to your products. General keywords are popular and therefore expensive, but many also drive the wrong customers to your site, and as you're paying for each click-through, you want to be sure that you're attracting the right people. For example, if you sell kitchenware, don't use the keyword "kitchen"; you'll get people who want a new kitchen, people who want to work in a kitchen, people who want kitchen curtains and much more. Better to use "cookware" or "kitchen knives", which will match with people who are looking for the stuff you're selling.

Remember to think about your market. If there are particular trends in the market that may influence how people search, use those keywords. Similarly, if your product or market is known by a generic or slang name, include that in your list. Use plurals to catch extra searchers and consider the combinations your keywords can make; you could use "kitchen knives" or "cooking knives" or "sharp knives for cooking".

Be aware of any words that are copyrighted or trademarked, as using them in your keyword list may land you with infringement problems. Above all, make sure that your keyword list - which should be at least 15-20 words or more - is carefully crafted to cover the product range you're trying to sell, and is targeted to the people you want to attract to your site. Regular monitoring of your market, your competitors and how your pay per click campaign is running will allow you to alter and refine the keywords as you go along, making sure that the right visitors are clicking through to your site.

Getting your keywords right and keeping them focused is an ongoing part of your pay per click campaign and, along with setting a timescale and budget, and frequent monitoring and measurement, should result in a successful project and more profits.