Preregistering a study is not the only direction to go when conducting a study. If you are writing a journal article, for example, you may want to see if your study has any merit before running the study. In these cases, you can submit a registered report to the journal instead.
Everything mentioned below is covered in greater detail on the Center for Open Science initiative page. It is highly recommended to read through this if you are planning to submit a registered report.
What is a Registered Report?
A registered report is a format that emphasizes the quality of the study's methodology by conducting a peer review before collecting data. As such, a registered report can be understood as a regular conference or journal paper with only the introduction, background, and methodology.
The standard paper lifecycle goes through the following phases: specify the hypotheses, design the study, collect data, analyze the data, interpret data, and then publishing the study. However, there are numerous questionable research practices that can find its way into a paper during this process. First, there might not be enough power, or sample, to detect the desired effect size. Additionally, as mentioned in the preregistration section, papers could be subject to p-hacking or HARKing if the results are undesirable. Additionally, publication venues may be biased towards some form of significant result or results that agree with the reviewers' opinions. The papers may not share their data or have their results replicated, leaving the paper to stand without any verification.
A registered report mitigates a lot of these issues by reviewing the paper before collecting the data, having the methodology of the experiment be accept by the quality or robustness of the study itself.
On Submission
If a researcher decides to submit a registered report -- containing the introduction and methodology -- to a journal, they go through an initial review process. If the reviewers decide to accept the registered report, whether immediately or after some revision process, the researcher is given an in-principle acceptance, or IPA. Afterwards, the study is conducted, to which the paper then goes through a second review process with the results and discussion. Some may be required to share their data and analysis scripts openly. The paper may still be rejected at this point, but if the study conducted is what was stated in the methodology, the paper will fully accepted for publication in the journal.
Some Additional Thoughts
Exploratory Analyses
You can still report on results that are not specified in the registered report provided they are marked as 'exploratory'. This makes a clear delineation what was part of the original study and what was not.
A Number of Directions
There are plenty of directions other than preregistrations or registered reports that may suit your needs better. For example, there are reports for explicitly exploratory analyses or posters that present the methodology of a study before data collection. Just be aware of all the rules and regulations on the track you decide to target.