#1. Useful Links
If you are new to SVN, these are the links that should help you:
#2. Quickstart guide for Cotonti developers
I'll consider the case you have 3 different locations: svn.cotonti.com, your local copy and www.test.com to test your code.
First of all you need to checkout the repository from svn://svn.cotonti.com to your [local]. You will get
branches: contains genoa branch and folders for plugin and skin developers, etc.
releases: stable releases kept for history
trunk: here the next generation of Cotonti lives
So, if you are going to work on the next generation of Cotonti, trunk is what you need. I have to mention that trunk is a development version, so it is normal if something doesn't work. From here and later on I will mean local/trunk and svn://svn.cotonti.com/trunk only.
Once you have checked out, you may copy trunk to your www.test.com and install it there as normal Cotonti for development. Yes, install.php is an installer script ;)
Then you edit your local files just as normal, upload them to www.test.com to test and so on just as you are used to.
After you have done something, you should commit your changes to svn.cotonti.com, so that files on server are up to date and other developers can sync with your changes. Use "Commit" operation on your local trunk copy. Here are some notes about committing:
Always "Update" your local with latest files from svn.cotonti.com before you commit. It's required to sync with what the others have already done. Keeping everything up2date is a must.
You can commit a single file, selected files, folders or entire trunk. SVN will grab only those files which were changed by you and save changes on server.
Write comments for your commits (also known as revisions or changesets).
Don't commit too often but keep everybody up2date. Usually you commit after you have done something logically consistent (e.g. completed a task, a few tasks at once) or if you want to save massive changes which will be completed later.
Keep your local repo copy clean. Remove temporary/testing files before commits or they will become a part of trunk.
If you want to undo all your recent changes, use "Revert local changes" svn command.
If you want to repair your local copy, you can use Clean command. If nothing helps and you still get errors, save your changes somewhere, recheckout the folder and apply the changes again manually.
Further reading related to SVN in Cotonti development:
How to properly update SVN
Guidelines to committing revisions
Guidelines for making any SQL changes