I use a ratio of 1 tsp of salt (kosher or sea salt) to 1 cup of water. When brining, I like to add in a couple of tablespoons of lemon juice and/or white vinegar.
Boil the jars to sterilize them. Wash the vegetables well and cut out any bruises or soft parts. With tomatoes, remove the seeds and surrounding gel. Some vegetables, like onions and potatoes, should be peeled. Most vegetables should be pickled raw.
Boil together a solution of salt and water (brine) and mix in some lemon juice or vinegar. Pack the vegetables into the jars well, but not so they are smushing each other. Pour in the brine and tap the jar to get rid of the air pockets. Place the capped jars into boiling water for ten minutes. Remove, and let them cool naturally (don't cool them by running under cold water, placing in the fridge, placing in ice water. This will cause the glass to shatter.)
Onions and tomatoes to be enjoyed for the months to come.
Soon, I'll write about making your own sauerkraut, which can be wonderful.