Great preparation does yield great results, and software quality assurance is no exception. Here are the steps I do every time I need to create a new test plan:

Step 0: Analyse the product
Ask the product owner about the launch and high priority features, since quality may have been sacrificed in favour of speed. Talk to the project manager to see if they have been facing recurring issues. Ask developers where technical debt risks turning into a point of failure.

Step 1: Define the scope
You usually focus on the level of testing (e.g. unit or system testing) and may additionally limit yourself by the types of testing. Functional vs non-functional testing is often quite a distinction in itself.

Step 2: List test criteria
Once you know what to look for, it’s only logical to define what constitutes QA success and failure. Feel free to introduce benchmarks that are relevant to the scope. Some examples include defect rate percentage, test case pass rate, and threshold of severe open defects.

Step 3: Map the environment
Write down all the tools that your team uses for software testing. Evaluate whether this suite is enough for the scope. Research and add new solutions if necessary.

Step 4: Create a schedule
Knowing the schedule of product and developer teams is 90% of creating your own schedule. Make sure to account for potential missed deadlines on both your and their ends.

Step 5: Write down deliverables
All that’s left now is to formalise the expected output. The test plan that you may be writing right now is a deliverable as well. So are the new test cases that your team will make as well as any fruits of the automation labour.

Learn more about each step in my article dedicated to that.