Toasted nuts have a completely different taste. Toasting them brings out the flavor. In fact, toasting makes it so that you don't have to use as many nuts in a recipe. It's hard to describe the difference...just try and you'll see.
Now to toast them. Set your oven to 350 degrees and grab the nuts you want to toast.
I'm toasting some to use to make granola. Get a cookie sheet or shallow baking pan and lay the nuts out on it. You don't need to grease it or anything.
Put the nuts into the oven. :) You'll want to keep an eye on them, but it takes around ten minutes. Depending upon the type & size of the nuts. You also want to shake them around or stir them with a spoon at least once during toasting. You can tell they're done because they'll be a nice golden brown and you will be able to smell them easily.
Now they're ready! Don't feel bad if you burn a batch....I refuse to admit how many I've burnt. Usually because I forget them!!!
You can also use a skillet to toast them. I use this method when I'm toasting pine nuts or something else really small. It's the same basic idea, heat a skillet to med-high heat until it's hot. Toss the nuts in (no oil!) and cook until brown and fragrant.