Archaeological experiments are their own beast, and there's no one-size-fits-all solution for their planning, running, and documenting. There are a few things that have turned out to be very helpful in my own experience, though.
When you're designing your experiment, the core thing to keep in mind is your experiment question, and everything else should be built around that. You will have to select tools, materials, and procedures that allow you to answer your key question. For each selection regarding tools, materials, and processes that you make, you must evaluate whether using a modern tool or process (which often can be controlled better, or ensure that each part or repetition is the same) or the historical tool or process will serve better.
Once your experiment design process is done, it has been proven very helpful to go through this experiment step by step in your mind and write down notes on what happens when and in what sequence, how long each step will take (approximately), and what tools and materials you need for each step. A test run might be even better, but in most cases, that is not feasible.
For the actual running of the experiment, the following template might help you - it was developed from our experiences running experiments at the European Textile Forum.
Template for Planning and Protocolling Experiments
Experimentor(s):
Tools and Materials:
List everything you will need here, down to puny things like pens (that hopefully will write on all the surfaces you need them to write on!) and labels. Don't forget the things you will need for documentation (including things like camera, colour control cards, measurement tools, SD cards for pictures, and something to backup your data).
General Procedure:
A short abstract/overview of the procedure comes here; this should include the question that is to be answered by the experiment.
Items On Hand after the Experiment:
Your outcome in terms of actual physical items – the things you will have on hand afterwards to make your measurements and analyses. This also serves as a check for you to see if your plan is in danger of growing too much, and as planning help to see how many labels etcetera you will need.
Experiment Schedule:
Preparation:
Any preparation procedures for the experiment go here – that is things that you need to do or get before running the actual experiment. Make this a list to help you have everything you need on hand. Preparation includes charging batteries of tools you may have to use, and checking that any tools are in working order.
Protocol:
This should be a detailed list of all the single steps necessary to perform the experiment. Writing down the protocol in detail, step by step, will help you catch holes in your plan, make sure you have thought of all things you need, and hopefully give you an overview of how long each step will take, and thus how much time you have to factor in for the whole experiment. Try to estimate how long individual stages will take, don't forget that things may need to heat up and cool down, that measuring will also take time, and that you may need a breather here and there. List your time estimates, and plan for some more time for running the actual thing.
Also list your documentation points and procedures in this protocol (e.g. “take photos”, “measure pH”) at the appropriate places. Make tables for your measurements, and leave spaces to fill in the time when you are starting and ending procedures. Remember to make spaces and tables large enough so you can write into them by hand!
Think of this like a very detailed recipe that you only need to follow when running the experiment, taking you through it step by step. Imagine that you are only writing the protocol for an entirely clueless other person who will run the actual thing instead of yourself! This may sound weird, but having everything you planned written minutely down in the protocol means you will be less prone to forget something in the heat of the moment, or when you begin to be tired, or when you get distracted. It also means you can clearly see when the plan and reality start to diverge.
Any tools and materials that you are going to use should also get listed in the “tools and materials” section above, giving you a checklist to run through before you get started.
When you are ready to go, print out your protocol. Make sure you have enough space between sections and/or in the margins to take notes. If your experiment includes liquids of any kind, print on a laser printer, not an ink printer.
And then – good luck, and may your experiment be fruitful!