I'm quite lame, so I usually forget how to set up a Subversion repository every time I need one. Here's how to do it, assuming the project is called "proj" and already exists in /home/joel/Src/proj

svnadmin create /home/joel/Src/svn-proj
cd /home/joel/Src/proj
mkdir trunk
mv * trunk
mkdir branches tags
svn import /home/joel/Src/proj file:///home/joel/Src/svn-proj -m "initial import"
cd /home/joel/Src
rm -rf proj
svn checkout file:///home/joel/Src/svn-proj/trunk proj

Oh, the trunk/branches/tags thing is optional - if you're only doing something straightforward such as managing configuration files on a single machine, you could get away with

svnadmin create /home/joel/Src/svn-proj
svn import /home/joel/Src/proj file:///home/joel/Src/svn-proj -m "initial import"
cd /home/joel/Src
rm -rf proj
svn checkout file:///home/joel/Src/svn-proj/ proj