1. Create a website. The website should have content as your content is what will drive traffic to your site. Your site should create value for visitors, and elicit their trust. They need to trust you enough to know that the products and services you are recommending is best for them — and they will do the action that you want them to do.
One of the common mistakes I see of newbies is they create websites for the sole purpose of earning from affiliate advertising, and their website ends up nothing but banners of various affiliates they promote. Their website has no value at all, just a bunch of advertising plastered here, there and everywhere with hardly any content. This approach is likely to fail because the website is not giving the customers a reason to be engaged with the site.
2. Check what types of website the affiliate program accepts. Some companies running affiliate programs refuse to accept sites using free hosting such as Geocities. If you are thinking of a blog, check if the company you want accepts blogs. And check if you can add/run scripts that the affiliate program will give you on the site you will set up (some blog platforms are harder to use in terms of adding scripts). No scripts means no affiliate program ads and no revenue.
Then you can decide on how you want your site hosted — whether you can start slowly and use a free hosting site or right from the start present a more professional image for the site with a paid hosting program. It is important to think of scalability — when your business starts to grow — and how it will affect your hosting needs. If you are in Geocities, and your site grows and now needs a better hosting platform with more bells and whistles, you may start from scratch again in terms of traffic generation because you will have a new domain name.
My suggestion is to get a real domain name, pay hosting and start the business right.
3. Select the affiliate program that is right for you. There are many affiliate programs to choose from. You can go to Commission Junction , Linkshare or Clickbank to see various affiliate programs in one roof. Or you can go to individual websites that offer these programs and apply.