ABOUT THE INGREDIENTS
Despite what ingredients you might find recommended in recipes online and elsewhere, prosphoro should only ever be made with flour, water, starter, and salt. Certain parts of the Orthodox world even recommend that the salt should not be added. Some folks add a few drops of holy water as a blessing.
Try to always choose flours that are certified ORGANIC. This ensures the flour is not bleached or otherwise treated with chemicals that adversely affect the wild flora. Always sift your flour in a fine mesh sieve. Insects and impurities are common even in the most carefully milled and fresh produce.
Insist on a high protein flour. Protein content over 12% is preferable. Depending on where you live, they are variously called "baker's flour"or "hard flour"or "yellow flour". In Greece they call it "type M". In Canada I think they label it "red flour". The 0 or 00 label refers only to how finely it is milled. You will struggle to achieve good results with just "plain flour" or "all purpose flour".
Many prosphoro bakers in Greece seek "stone ground" flours "of the mill" (known as "tou milou"). The process of stone grinding as opposed to steel roller milling, produces more flavoursome breads.
Very importantly, know that every flour type behaves differently. And every starter made with a certain flour, will behave differently with different flours. It is wise to use the same flour for both your starter and your baking. If you need to change your flour, try to help your starter adapt slowly over a number of days of feeding with increasing percentages of the new flour in the mix. Ideally, until you have travelled a while on your prosphoro journey, try to keep this variable constant.
If you purchase flour in larger quantities, store your surplus in airtight containers in a freezer. Even three days in a freezer should kill any insects. Storing flour longer term at cold temperatures helps maintain freshness. Make sure you allow the flour to come to room temperature before using it.
Tap water should be OK in most places, provided it is not heavily chlorinated. If your tap water is chlorinated, it will kill the microbes essential in the leavening process and you will not succeed in producing a vigorous starter.
Even with a healthy starter, if you add chlorinated water to make your dough, there is a strong possibility it will not rise well, or if if it rises, it might take much longer.
I was surprised how effectively one dose of tap water killed my first starter on it's third day feeding.
You can lessen the chlorine content of tap water by either boiling it and allowing it to come to room temperature, or "airing "it in an open container overnight before use.
Personally, I find the non-aerated, natural spring water in bottles the most convenient. I always use this water now, especially after the 'accidental death of my first starter. Do not use distilled water, since the microbes do best with the trace elements found in water.
To avoid large crystals of salt remaining undissolved in the mixture, try to use fine salt (or grind it finer). Remember that 'table salt' has anti clogging agents added. Choose sea salt or cooking salt instead.
ABOUT THE UTENSILS
Wherever possible the good quality utensils you use for prosphoro should be set aside solely for that purpose.
Try to avoid using plastic containers. Ceramic and glass are best as storage containers and water jugs.
Since we knead a firm dough, a good quality, heavy glass or ceramic mixing bowl is more stable and easier to use than a lightweight plastic or even metal one. And they can be cleaned more thoroughly.
You will need a 'fine' or 'very fine' mesh stainless steel sieve.
A rolling pin helps with the kneading process but is not essential.
The best baking pans are the round aluminium pans with tall sides. (Handling a short sided pan with the dough risen high above the edges can be difficult).
Some people like using non-stick pans. We don't know how reliable, chemical free and safe some of these are so we avoid them.
Most digital kitchen scales are very accurate and reliable. You will need to measure down to gram weights (eg salt) so digital scales are best.
Bamboo skewers are used to pierce the prosphoro before the rise.
A good quality cooking/basting brush which does not shed hair.
Some BPA-free plastic bags (freezer bags) are useful.
Cotton or linen tea-towels.
A woolen blanket.
Kitchen paper towels.
A clean, sharp needle (for releasing gas from any air bubbles that develop)