In my project, I started by choosing one of the many open source licenses (went with Apache 2.0 ). Then I added the file LICENSEto my project, copied / pasted the license there, and made the “necessary” headers for each source file.
After that, I chose the project platform (or watchamacallit). I skipped SourceForge and chose Google Code instead , later moved to Assembla + GitHub . I put my source in the provided SCM system (first SVN , later Git ).
Alas, the difficult part is not choosing a license, not getting your source to the public, documenting your things on a wiki or writing tickets. The hard part is to create a (successful) community around your project. To do this, you need an interesting project, people who are interested in your interesting project and platform for connecting these points together. The silence of good luck and / or reputation does not hurt, not least.