Lately I've been thinking a lot about the best way to enter an existing project fast. I've written some of my thoughts here, and would really like to hear advice from other people.
What are the things you find a must?
I'm especially interested with open source projects, if there's any difference.


It sounds good. I would add the fact that he/she should read the current documentation on the project.

+1  A: 

Of course any (recent) documentation would help.

The most important for me would be the design of the model (something like UML diagrams). Once I get that, I can get a very good understanding of the project. If it is not available (because it was not done), then the database schema can help understand the relations between the different objects of the project. Having a conversation with the other developers involved is also a good start. After that, I guess just digging through the code would work.

+2  A: 

Reading any current documentation (code included) is a great place to start, but I'd say that finding a good mentor might be your best bet. Finding someone knowledgeable about the project that is willing to help guide you through the project for a while and help lead you to answers to your questions will help you get on your feet the fastest.

Sam Merrell