All research should start with a protocol. A protocol is a document that lays out what question you're trying to answer, why it's important, and how you plan to answer it. Creating a protocol is an important step in ensuring that your research is rigorous, ethical, feasible, and reproducible.
A growing number of journals, granting bodies, and research ethics committees require the completion of a protocol prior to beginning your research. Even if you aren't required to draft a protocol, creating a protocol can save you time and resources, reduce research waste, keep you accountable, and ensure that you and your team are adequately prepared.
The specific requirements for a protocol are a little different depending on the type of study that is being planned, and depending on whether the protocol is to be published, registered, or kept as an internal document for the team to work from.
In all cases, writing your protocol is great preparation for your final manuscript. Like a journal article, your protocol should detail your research question, background information on your topic, your data collection and analysis methods, and limitations. Additional information for the protocol may include budget, timelines, and safety and ethical considerations.
Once you've written your protocol, consider publishing or registering it. Doing so allows you to stake your claim on the topic and gives you an additional publication for your CV.