Wash the peppers, then while wearing protective gear (a latex or vinyl glove), carefully slice the peppers in about 3/8" slices. If you want mild peppers, put the slices in a colander and rinse away as many of the seeds as you can. Loosely pack the slices in your jar(s), adding the garlic slices if desired
Put the vinegar, water and salt in a non-reactive pot on the stove and heat to a boil.
Place the jar in a large bowl or other dish in the sink and CAREFULLY pour the hot vinegar mixture in to the jar or jars holding the peppers until they are covered. You may have slightly more liquid than needed.
Let the jar sit out on the counter to cool off for about an hour before covering and placing in the fridge. They will be ready to eat in about three days.
While they will easily last about 8 weeks or more in the fridge, after about 3 weeks they do start losing a lot of the crispness that I like. Depending on your personal tastes, and how often you use them, you may want to try making a half-batch.