The Procedure ...
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The procedure is how you plan to do things: how you are going to conduct your experiment.
An experiment can only have one variable. That means you can only change one condition in each experiment.
For example, with the seed-sprouting experiment, if you vary the temperature at which the seeds are stored before you plant them, keep each group of seeds at that temperature for the same amount of time. And make sure all of the seeds get the same amount of light and water after you plant them.
If there's more than one variable, the experiment becomes flawed. It can be hard to figure out what other conditions must stay the same. But it may help to think it through before you start your experiment.
Also think about how long your experiment will take before you decide on your procedure. If you only have a few weeks to do your experiment, don't decide on a procedure that will take months to carry out.
Think about your "sample size." How many seeds will you test at each temperature? Allow a big enough sample so you can have a few duds in each group.
Once you decide on a procedure, write it down step by step. That way, you can prove what you did and can follow the same procedure if you need to repeat the experiment.