Hi, take a look at this example, credit to Ken Potter. I've found that every coin series has a different look to its doubled dies, but the general principles are the same. There are a few good posts on the difference between MD and DD, and here's a good one on doubled dies.
Here's one of my favorite DDOs I've found on an 1887 Indian Head cent:

Here's one of my favorite DDOs I've found on an 1887 Indian Head cent:




















