Assuming you're starting from a fresh pack, make the starter 4-5 days before brewing. After about 24 hours on the plate, it should have fermented out. Once it's finished, just stick it in the fridge. When you're ready to pitch, take it out of the fridge and pour off as much "beer" as you can without pouring out any yeast. Swirl up what's left and pour it into the fermenter. If there's any yeast left, pour some wort or pre-boiled water in and swirl until you have most of it in suspension, then pitch.
If the pack is more than a couple months old, give it an extra day on the stir plate, just in case. A few extra days in the fridge won't do any harm. Much worse to make the starter too late and have to postpone your brew day. I'm assuming you're starting from a very fresh pack; otherwise MrMalty would be recommending a larger starter.
Edit: Or, you know, what he said.