Never made any custom content before? Start with the easiest, most basic stuff (which you can make with all free programs) - Sims 2: Walls, Floors, and Ground Cover, Sims 3: Custom Patterns
Just installed the Sims 3 patch or about to? Read this article for helpful advice about patching and keeping your custom content working!
It's 2012 and I can't believe I got into creating custom contents only now!
I started with make-up 'coz I'm a fanatic of make-up designs.. I'm absolutely trying to learn how to do hair and other type of accessories so I can make a complete H2T (head to toe) Sims models.. I'm so excited! =)