Think I've made a topic similar to this, but just want to check am doing this right. I use my MacBook unplugged. When it get's to around 10%, maybe less... sometimes it's in the 20's, I plug it to charge. Sometimes I leave it in if am doing intensive work, otherwise, when it's 100% I unplug it. I never let it drain completely so it turns off, though it has once or twice just cuz I couldn't get to my charger. So yeah, am I doing this right? Just wanna make my battery last. I have a late 2011 base model MacBook Pro.
You don't always need to let it get down to 10 to 20% if you know you're going to need a full charge. Also, do make sure you get it charged asap if you let it run down to empty. In general, the above linked knowledge base article if your best guide.
Run on battery when you need to and plug it in whenever you can. It doesn't matter at what percentage you plug or unplug. Just make sure you're not running on AC power all the time, as your battery needs to be used to stay healthy. This should answer most, if not all, of your battery questions: Apple Notebook Battery FAQ The built-in batteries in the newer Mac unibody notebooks come pre-calibrated and do not require regular calibration like the removable batteries.
i keep my battery plugged in whenever its sting on my desk and have never had an issue. I recommend that your try the same, leave it plugged in and let it charge completely.
Problem is if you do that for a long period of time, when you actually want to use the battery, you may find it doesn't work so well for you.