How can you recover digital photos once they are deleted?

Trying to learn more about iphones, since I just got one for my birthday, I headed online to read some FAQs about them. I found that there are lots of resources out there to help with any technical difficulties like recover deleted pictures from iphone folders. That's great news to me because I am well known for needing help with my tech gadgets. I have lost files more than once already, so knowing ahead of time that help is available makes me feel much more comfortable with my new device. Now I am trying to find a free user's guide.