For the crunchiest pickles, select firm, dark-green pickling cucumbers that have not started to ripen to white or yellow. Cut them into spears or slices, as desired (left whole, they will take a long time to pickle in the fridge). To increase the crunchiness, you can sprinkle the cut cucumbers with a couple of tablespoons of salt, let them sit for 2 hours, and then rinse and drain before proceeding, but this step isn't absolutely necessary.
Prepare a quart jar with a lid by running it through the dishwasher or washing it in very hot soapy water and letting it air-dry. Any jar with a lid will do; the wider the opening, the easier.
Place the dill in the bottom of your jar; peel and crush the garlic cloves (if using); add the onions (if using) and drop that in along with the peppercorns (if using); then put in the cut cucumber. Mix the salt, vinegar, and water in a separate container, stirring until the salt is dissolved, then pour it over the cucumbers, filling the jar right to the top.
If you're in a hurry to enjoy your pickles, heat the vinegar, water, and salt to a boil before pouring it over the cucumbers (just know that heating unpasteurized vinegar kills off the healthy probiotic bacteria that make pickles good for you).
Pop on the lid and put the jar in the fridge, and they will last for up to three weeks.
Variations: Try Dilly Snap Beans, Dilly Zucchini Strips, or a medley of whatever veggies you have on hand. Try adding different herbs and spices, jalapeños and anything else that looks good at the market.