I've got several basil plants this year and they've been growing like crazy... producing far more than I can use or even give away at the moment. So, I decided to take some of it and freeze it for use later on. There are several ways to do this. Do a search on Google for "freezing herbs" and you'll find countless pages on the subject. This is the way *I* freeze herbs for later use... I don't pretend to say it's the only way... but the way that I've found works best for me.
I took several bunches of basil and discarded the stems, leaving only the tender leaves. I washed the bunch and spun them dry using a salad spinner. I placed the bunches of basil leaves in my food processor with only a tiny bit of water and processed it until the basil was chopped quite finely. Once that's done, I fill ice cube trays with the basil and water mixture and freeze until solid. Finally, I pop the cubes from the tray and place them in labeled zip-lock freezer bags. I go by the rule of thumb that the basil cubes will be at their peak for about 6 months when frozen. Of course they will keep longer than that... but it won't have as fresh a flavor as the first 6 months of storage.
These small cubes I made are about a teaspoon each when thawed, if I use the larger trays, it's about a tablespoon. Fill one of the compartments on your tray and measure the amount so that you'll know about how much herb you have in each cube.