Use sea salt you can buy in bulk at Central Market. It's a fine grain, dissolves easily and isn't iodized. Mix 1/3 cup of salt, 1/3 cup of baking soda in a small container that stays on your counter with your neti. The baking soda softens the water and you're less likely to get that burning you mention. Plus...baking soda gets rid of odors, so you're nose is like a sparking clean...nose.

When you put water in make sure it's warm by running it over your fingers from the tap. If it's warm to your fingers it's the perfect temp.