Preprint Best Practices in Computer Science
The best practices I've seen in sciences, including computer science, involve


making the pre-print available upon/slightly before submission of the manuscript to the journal/conference,
publish the pre-print on the repository where the manuscript fits in thematically, i.e. where you find most pre-prints you read/cite (like arXiv oder Zenodo), or use your institutional repository, and
update the pre-print with the post-print (the version after peer-review but without the journal/conference layout) if allowed by the journal/conference, so that you have one or two versions available.


You can check whether you're allowed to update you pre-print with the post-print in Sherpa/RoMEO, on the journal/conference webside or in the copyright transfer agreement you have to sign upon acceptance. There is also statet what other conditions apply, e.g. whether a link to the published version is necessary or you have to use a specific licence and so on.