Step 1:

You go to Clickbank's marketplace and scan around the top 2 pages of each category. Take a look at the statistics of these products.

By this I mean the gravity, the % referred, $ earned per sale etc...

So you think you've found a good category to enter - Say Sports & Recreation. The next logical step would be to unearth a winning product to promote.

Generally, the top 5 products are extremely competitive and have tons of affiliates promoting it already. It would be quite difficult for you to take on the competition at this stage.

Step 2:

Click through to the next few pages and look for items with a reasonable % referred that isn't too high and a good gravity weighting.

Broadly speaking, a % referred rate of more then 75% is high and anything with a gravity rating above 30 would be worth a shot.

Step 3:

Select 3 products that fits the criteria and choose from them. Click on "view pitch page" to see the sales page for yourself. It'll instantly become very clear to you which of the 3 sales page converts better.

First, I do a "look" around Clickbank Marketplace. I look from the first page (best sellers) onwards slowly to the back. You would notice that most are around the same niche but I need something different, something that is a niche and does not have many similar products in the Clickbank marketplace...

Other things to look out for:

1. Does the vendor provide a strong affiliate resources page?
2. Is the % earned per sale stat high? Generally, I'd never promote a product that pays below % 50 unless it's a high ticket item.
3. Are there any payment leaks? Scan for them, it's extremely important that you do this.

I've to mention there is no sure-fire way to select and pick products to promote.

Even if you follow what I say to the dot, you could end up picking a loser, the only 100% guaranteed way is for you to test it out - Find what works and what doesn't yourself...