Preregistration is the practice of documenting your research plan at the beginning of your study and storing that plan in a read-only public repository such as OSF Registries or the National Library of Medicine's Clinical Trials Registry.
This combats the file-drawer effect, by making more studies discoverable to future researchers who may want to go down the same path, and can also reduce false-positive inflation. Preregistration can be useful for exploratory studies, but mainly benefits confirmatory/hypothesis-testing research.
How do I pre-register a study?
Take advantage of an existing service like the OSF. Preregistrations are often not small documents - your pregistration main contain your literature review, any pilot studies performed, any existing data informing the work, and a full list of research questions and hypotheses. If your research will involve human subjects, your recruitment and inclusion criteria should be part of the preregistration as well.
Services like the OSF and clinicaltrials.gov have online forms to make the process easier and to make sure all the necessary information is present.
Registered Reports build on pre-registration by flipping the standard publishing process of submitting a paper once the research is completed. The introduction and methods sections of a paper are submitted before the study is carried out and is peer-reviewed and accepted for publication at that time. Once the study is conducted, the rest of the paper is written and published in the journal - regardless of the study's outcome. This helps mitigate many forms of bad science, such as p-hacking and HARKing, but additionally means that well-designed studies with null results still get published.
"Registered Reports is a publishing format that emphasizes the importance of the research question and the quality of methodology by conducting peer review prior to data collection. High quality protocols are then provisionally accepted for publication if the authors follow through with the registered methodology.
This format is designed to reward best practices in adhering to the hypothetico-deductive model of the scientific method. It eliminates a variety of questionable research practices, including low statistical power, selective reporting of results, and publication bias, while allowing complete flexibility to report serendipitous findings." - Center for Open Science
A research protocol is a detailed study design and/or set of instructions for carrying out an experiment, usually in as much depth as possible. This is a more-detailed document than the methods section of a paper.
Sharing a complete protocol openly promotes replicability, transparency, and helps reduce waste in duplicated effort. There are several ways to share complete protocols.