There's a lot of great info on lacto-fermentation out there but I wanted to put together a list of the key ideas I've found most helpful and share with others often.
If you really want to get into this stuff, check out academia.edu and search for kimchi, sauerkraut, soy sauce, kombucha, etc. and you'll find some golden nuggets of info.
Couple of rules of thumb and general lacto-ferment related ideas:
Heads up, when I talk about salt percentages, I mean combining the total weight of the veggies AND the weight of any water used for brine and multiplying that by the percent.
So if you’re making lacto-fermented green beans at 3%, take the total combined weight of the green beans (and any other veggies used, like garlic) and the water used for brine, and then multiply that by .03 to get the amount of salt needed.
When fermenting cabbage and other veggies in that family, go with 2% salt.
Root veggies like beets and radish: 2.5%
Cucumber pickles: 2.5 - 3%
Green beans, snow peas: 3.5%
Obviously, experiment and all, but don’t go near 5% or higher unless you know why you’re doing it. And don’t go under 2% if you’re doing a straightforward ferment with just veggies and salt.
Unrefined sea salt is great because of its mineral content. But it's not completely necessary, but never use iodize table salt. I highly suggest using Calcium Chloride, it really really helps keep veggies crunchy.
When I’m making kimchi and sauerkraut, I like to do 2% salt and .25% calcium chloride. For lacto cucumber pickles, I use 2% salt and .5% CaCl.
Letting your ferments de-gas is very important. The easiest way to do this is to use an airlock. It’s also helpful to open up a ferment and stir it around a bit so that unpleasant volatile compounds can escape. During fermentation, especially when fermenting veggies in the brassicaceae family, hydrogen sulfide forms and it stinks. But you can decant your ferment and get rid of it. But if you keep your ferment sealed, the trapped H2S can convert into mercaptans which are not volatile (so you can’t get rid of them) and it will taint the batch.
If you keep your ferments sealed up and don't de-gas, you may also cause “pickle bloat” and end up with a texture mess.
When looking for recipes, look for recipes that are “grammed out.” If you find someone that’s using grams and percentages, you know they’ve put the work in to figure things out. But there are a ton of great recipes and ideas out there that use volume measurements too.
A great way to ensure good clean ferments is to use ingredients with anti-microbial properties like garlic, hot chilies, and ginger (think kimchi), and herbs and spices like bay leaves, oregano, allspice, and cumin. Using these will prevent unwanted activity and flavors from developing, allowing the lacto-fermentation to shine.
For example, sauerkraut fermenting without these added ingredients and being exposed to a little too much oxygen and high temps may form diacetyl. Diacetyl actually tastes pretty good to some people. It's creamy and buttery and use to be used as an artificial flavorant. But it is a flaw, I don't like it in my sauerkraut at all, and it's potentially harmful to your health.
For more on kimchi, check this out.
For more on hot sauce, check this out.