Though a preprint could be circulated through any medium in principle, in practice, fields often establish central repositories that disseminate manuscripts further, for example by notifying interested community members, and screening uploaded content. There are several such repositories or preprint servers.

To benefit best from the additional exposure a preprint gains, you'll probably want to choose a location based on where your manuscript will find the largest number of interested readers. For psychology, the Society for the Improvement of Psychological Science has established PsyArXiv, which has since been named the APA's preferred preprint service.

Other fields have a long tradition of preprint publication and established central repositories, especially arXiv for physics, mathematics, and computer science. Because preprint submission is so common in these areas, some journals allow for submissions directly through arXiv. The Open Science Framework provides a domain-general service for preprint repositories, which powers a number of preprint repositories.