Find an Affilate Product

Firstly, there are no guaratees in affiliate marketing.  Do not believe claims of huge income without work or study.

You will have to your homework, web searchs and comparisons.  There is software out there that can do that for you, but it is costly.

Clickbank  is an easy to join program with thousands of digital products.  Look for products with high gravity. Gravity defined by clickbank, "Number of distinct affiliates who earned a commission by referring a paying customer to the publisher's products. This is a weighted sum and not an actual total. For each affiliate paid in the last 8 weeks we add an amount between 0.1 and 1.0 to the total. The more recent the last referral, the higher the value added."

That doesn't mean that low gravity items won't sell, it just shows how other affiliates are faring, and the items with high gravity mean higher sales competition for you.  There may be new products that will become popular. 

If you have a particular area of expertise, new products with a lower gravity may be profitable if you create blogs and can write insightful and intelligent copy about the product.

Paydotcom  is another easy to join affiliate program and they have a list of top sellers.  Again there is more competition for sales of these items.

Shareasale,  is another site that has hundreds of affliiate products.  They list their top 100 sellers. They usually require a website and some of their merchants must approve your application to promote their products.  Many of their products have RSS feeds and widgets that you can add to your blogs or websites.

There are many such programs on the internet including Amazon and Ebay.  Amazon now even has an free astore feature which you can use to create a specilized store of Amazon products on your website which you can also get for free with Bravenet or Freewebs.  I am sure there are others if you just do searches.  At last report a free service called Auctiva may be used to build an small eBay store.  There are charges for eBay listings.

There are many top quality afiliate items that do not convert well because of poor webpage presentation or ad copy. What you need to do is find some likely top selling items, then use all the free advertising methods you can find to test the waters.

If you can find the conversion rate that is also important.  That is the rates of sales per click on a website.  The higher the rate the more popular the product.  A good policy is to pick a few products that are appealing and then use free advertising.  If you start getting lots of hits and make a sale or two, then use more free advertising, purchase featured ads or more costly advertising to promote the product.