This will be a post-in-progress for a little bit. I am currently sprouting two basil plants for a pruning comparison, just to show what a difference proper pruning can make. However, in the meantime, I can show the basil trimming basics.
Before we begin, an important Don't. Don't pick individual leaves from a basil plant! Your plant requires leaves to produce the sugars and energy it needs from photosynthesis, and since you will be taking the tips, it needs the older leaves left in place. The exception to this, is if the older leaves are sufficiently large that they are overshading the rest of the foliage; you can remove them in that case, but make sure there is other foliage. You should never take it down to nothing but stem or only stems and immature buds. If you are wanting periodic small harvests, just let the tips grow larger than buds before removing them; you can take up to ⅓ of the plant at any one time without trouble, but that doesn't mean it has to be for each branch; so, once you have two branches, you can let them get to 5 or 6 nodes long and then cut down to 2 on one branch if you leave the other intact for a while longer, and so on.