Marketing an online business is essential to its success. Building a decent e-commerce website is relatively easy - but attracting the right people to the site at the lowest possible cost per visit, and persuading the highest possible number to spend the maximum amount, on repeat visits, is the difference between a profitable online business and a virtual white elephant.

Your planning should start with a market appraisal. You can use keyword research to identify how many people are searching for the products and services you're planning on offering. The research, if you use a service like www.wordtracker.com, will also tell you how many web pages are competing for the phrases that people are using.

Competitor research is important. If you are to persuade more people to buy from your online business rather than from your competitors, you need to offer a more compelling marketing proposition than them.

Marketing is an investment. Your budget needs to be sufficient to enable you to test and measure a range of traffic building and sales conversion tactics over a period of at least 3-6 months. When you have tested how well your site converts visitors to customers, you will be able to calculate how much you should pay for a visitor. Paying more than your breakeven figure - your sales conversion rate multiplied by your average gross profit per sale - will be unprofitable. That may be acceptable while you build market share but you won't want to continue with such a strategy forever.

There are a range of online and offline activities that you should include in your marketing plan - from pay-per-click advertising and search engine optimisation to affiliate marketing and opt-in email subscriptions. The critical thing to include in all of your online business planning is to set aside time for testing and measuring. The tools that you'll need are available for free. Google provides a very good Analytics service that will tell you how many visitors you get, where they came from, the keywords they used to find you and so on.

Finally, don't forget that you need to plan for all the usual activities that are essential to the running of any business, online or offline. Customer service, delivery systems and returns policies are just as important as getting new customers - a happy customer is more likely to buy again.