Suggestions for plugins, best practices, etc. welcome.
Just saw this article the other day:
They provide a tutorial and suggest using the following plugins:
The tutorial also has some code snippets that you will need to add. I haven't tried it out, but it would be great if you came back and posted your results, as I'm sure many people would find it useful. There are also a number of commercial products solely for this purpose; just google "affiliate platform Wordpress".