The key to success is to choose the right program, right from the beginning.
While it might be tempting to go for the program that pays the highest commissions, the program won’t pay you a penny if your visitors won’t go there or won’t buy once they get there. You have to be certain that the service you’re promoting is of genuine interest to the kind of visitors you get to your website, whether you’re buying them from search engines or anywhere else.

Sure, you can work backwards: You find a high-paying affiliate program and create a small site to send users to it, but do you know where to buy traffic for a program like that? You’re going to have to research the field, check out the most popular sites, and negotiate banner campaigns and link exchanges.
That’s fine if you want to invest the time and the effort. But it’s much easier to find an affiliate program operating in a field you’re familiar with, and use that program to earn extra cash.

For example, suppose you had set up a dating site. You might make some money selling subscriptions, but you might make even more by joining Match.com’s affiliate program and referring your visitors to them. Unless you’re planning to be the Internet’s biggest dating site, you’re not going to be able to compete directly and beat them, but you can help them — and make money doing it.
Or rather than sell your users directly to a competitor, you can look for services that complement your own. Visitors to your dating site, for example, might be interested in buying flowers, books on relationships or tickets on singles cruises. Instead of selling just one product such as membership subscriptions, you’d be selling a whole range of different goods to the same people and increasing the sources of your income.

Here are some tips to selecting an affiliate program that is lucrative and right for you:
Don’t accept less than 25% commission. You can find affiliate programs with great payment structures and high percentages of the purchase price in just about every field. In fact, many affiliate programs pay out 50%-75% depending on the type of product.
Look for comprehensive statistics pages that list the number of click-throughs, sales and earnings so you can see how you’re doing The information should be broken down by month.
Look for programs that offer a wide variety of promotional tools to put on your web page, including text links, banners, articles, brandable ebooks, etc.

Find out how often you will be paid and make sure that the payment schedule meets your expectations. Some programs pay biweekly, many pay monthly, others quarterly; which is best for you?
Look for examples of marketing methods that successful affiliates are using to get the best results.
Make sure that top level support is given. If they can’t answer your questions promptly and intelligently, you don’t want to work with them.