I just jumped in a project, and the project is maintained in SVN. However it does not have trunk directory, and now I want to do some experiments on the project, but I don't want to interfere with other people's work, then I think I should make a branch, but I can not reorganize the project with a new trunk, then what's the best practice to make a new branch based on project without trunk directory?
trunk is just a conventional name. If everything is at least contained in a directory (and not directly at the root), you may create a branch of this directory. If everything is directly under the root, talk to your colleagues and decide to follow the best practices with them: move everything under a trunk directory.