In Rails land at least, a lot of relatively inexperienced developers tend to have trouble when they can't google for the thing they want to implement or find it in the docs. I find that if I open up the source in roughly the area in which I need to implement something, a hook point is provided at about the right level of abstraction. Your mileage with other frameworks/environments may vary.
* Bundle comes with a `bundle open <gemname>` command that opens up the gems source code in whatever your shells $EDITOR is set to. I use this at least three or four times a day.
* Pry (an IRB alternative) will tell you the file + line of the definition of the method you'd be running if you ran `show-source some_object.some_method`. You can also `ls` and `cd` your way around ruby modules/objects which has been invaluable.