Before You Start

Pick a tested recipe, not a guessSalt ratios and timing are what keep the ferment safe, so start from a source like the National Center for Home Food Preservation rather than eyeballing it.
Get a food-grade containerFood-grade plastic and glass containers are excellent substitutes for stone crocks, and other 1- to 3-gallon non-food-grade plastic containers may be used if lined inside with a clean food-grade plastic bag. Never use a garbage bag as that liner — be certain foods contact only food-grade plastics, and don't use garbage bags or trash liners.
Know that Mason jars work fineFermenting sauerkraut in quart and half-gallon Mason jars is an acceptable practice, so you don't need a crock to get started.
Buy a weight to hold produce under the brineVegetables exposed to air are the main way mold and scum get a foothold, so a fitted weight (or a water-filled bag) matters more than the container it goes in.
Set aside a loose-fitting cover, not a sealed lidThe ferment needs to let gas escape while keeping dust and bugs out.
Pick a spot with a steady temperatureThis decides how long fermenting takes, not just how it tastes.

Setting Up the Ferment

Wash and trim your produceFor cucumbers, wash cucumbers, cut a 1/16-inch slice off the blossom end and discard it, leaving 1/4-inch of stem attached (the blossom end holds enzymes that soften pickles).
Weigh or measure salt precisely rather than eyeballing itToo little invites spoilage, too much just slows fermentation, but wildly off amounts in either direction are the main cause of failed batches.
Pack produce and brine into the container, leaving room for bubbling
Add your weight so everything stays fully submergedAnything poking above the brine line is at risk of mold.
Cover loosely and label the container with the start dateYou'll need it to judge doneness later.
Know that these ferment faster and stay in the fridge rather than being processed for shelf storage if making refrigerator style pickles

Set the container somewhere out of direct sun, ideally on a tray to catch overflow
Match your patience to your temperatureStore where the temperature is between 70ºF and 75ºF for about 3 to 4 weeks while fermenting, though temperatures of 55º to 65ºF are acceptable but will take 5 to 6 weeks.
Check in every day or twoPress the weight down if brine level drops, and skim any surface scum you see.
Expect the timeline to vary by foodRegular dill pickles and sauerkraut are fermented and cured for about 3 weeks, while refrigerator dills are fermented for about 1 week.
Toss the batch if you see fuzzy mold, pink or black discoloration, or a foul (not just sour) smellSurface yeast scum can usually be skimmed off, but real mold or bad odors mean start over, don't try to rescue it.
Taste-test once it's reached the expected timeTexture and flavor, not the calendar alone, tell you it's ready.

Decide between fridge storage and shelf-stable canning nowThis determines your next steps and how long the batch will keep.
Move the finished ferment to smaller containers or jars with tight lids and refrigerate if for fridge storagePlan to eat it within a few months for best quality.
Process in a boiling-water canner if for shelf stable jarsPickle products are subject to spoilage from microorganisms, particularly yeasts and molds, as well as enzymes that may affect flavor, color, and texture, and processing the pickles in a boiling-water canner will prevent both of these problems.
Use proper jars and lids for canningStandard canning jars and self-sealing lids are recommended, and processing times vary by recipe and jar size, so follow the recipe's specific times rather than a generic guess.
Leave correct headspace when jarringHeadspace for pickled foods should be ½ inch.
Let sealed jars cool undisturbed for 12–24 hours, then check that lids are sucked down and sealed before storingReprocess or refrigerate any jar that didn't seal.
Label finished jars with contents and date, and store sealed jars in a cool, dark spot for best quality within a year