Word of Caution: Take time to read the affiliate agreements
Word of Caution: Take the time to read the Affiliate Programs' Agreements before you join.
I applied to an affiliate program last month and as I read through the long and tedious legalese of their agreement, I came across the one thing that made me decide then and there to shelve them. It was a clause that demands that I share my WordPress password with them so that at any time that they are examining my website, they can go in and make their desired alterations. I couldn't believe my eyes. I was really glad I had persevered with reading all that legal stuff, painful as it was. Many times, I was tempted to just skip to the end and click the "I accept" button. I'm sure many affiliates did just that.