There is no general answer, because every project has a different workflow and culture. If you would like to hack on my little command-line bug tracker the answers would be like this:

- checkout the code from GitHub http://github.com/beza1e1/later

- use the "later" executable itself to find out, what issues are unresolved (e.g. "Web frontend")

- get familiar with the code base and especially the plugin architecture

- write some code (with whatever IDE or editor you like)

- send me a message, when you have something to look at

- after some reviewing (and probably changing) we can merge your code into the mainline

- Congratulations!