depreciation and taxes

[Maria D'Aura]

I've been using Turbo Tax for our taxes for years. It wasn't until reading BP and hearing the word depreciation that I realized my returns have probably been wrong for several years. 

Can someone point me to where I can learn about deprecation and what I need to look for on my return to figure out if TurboTax has been doing it or not?

If not, do I go back and amend returns? Maybe time for a CPA so any recommendations are appreciated. I'm in California and rentals are all in California if that matters.

Thanks