Actually you ignore the what the recipe says and use a hydrometer. I usually recommend for new brewers who are contemplating racking to secondary to check it after 12 days since you pitched the yeast
then again on the 14th day and if the gravity hasn't changed you can then rack.
Or you can do what many of us do and leave the beer in primary for a month to let the yeast finish and clear the beer.
In Mr Wizard's colum in BYO recently he made an interesting analogy about brewing and baking....He said that egg timers are all well and good in the baking process but they only provide a "rule of thumb" as to when something is ready...recipes, oven types, heck even atmospheric conditions, STILL have more bearing on when a cake is ready than the time it says it will be done in the cook book. You STILL have to stick a toothpick in the center and pull it out to see if truly the cake is ready.....otherwise you may end up with a raw cake....
Not too different from our beers....We can have a rough idea when our beer is ready (or use something silly like the 1-2-3 rule (which doesn't factor in things like yeast lag time or even ambient temp during fermentation) and do things to our beer willy nilly....but unless we actually stick "our toothpick" (the hydrometer) in and let it tell us when the yeasties are finished...we too can "f" our beer up.
The only way to truly know what is going on in your fermenter is with your hydrometer.
Like I said here in my blog, which I encourage you to read, Think evaluation before action
you sure as HELL wouldn't want a doctor to start cutting on you unless he used the proper diagnostic instuments like x-rays first, right? You wouldn't want him to just take a look in your eyes briefly and say "I'm cutting into your chest first thing in the morning." You would want them to use the right diagnostic tools
before the slice and dice, right? You'd cry malpractice, I would hope, if they didn't say they were sending you for an MRI and other things before going in.
That's how you'll know when to rack...or you can do like a lot of us do, and leave your beer in primry for a month then bottle.
We forget this simple fact...We are not making koolaid, or chocolate quick, just stirring in and having instant gratification...when you pitch yeast, you are dealing with living micro-organisms...and they have their own timetable, and their own agenda. No recipe can really tell you when a beer is really done.
And just because it is done "fermenting" doesn't mean that the yeast is done doing their job. They are very fastiduous creatures who like to clean up the mess they make during fermentation...the stuff that if you rack too soon can lead to off flavors. That's why a lot of us don't secondary and instead leave our beers alone for 3-4 weeks, then bottle...and only secondary if we are dry hopping, adding fruit, or oak. And even then we usually wait 10-14 days before moving our beer.
So don't be in a rush, this is a patience game, and your patience will be rewarded with great beer.
In fact even John Palmer mentions the benefit of not moving the beer right away.
From How To Brew;
Leaving an ale beer in the primary fermentor for a total of 2-3 weeks (instead of just the one week most canned kits recommend), will provide time for the conditioning reactions and improve the beer. This extra time will also let more sediment settle out before bottling, resulting in a clearer beer and easier pouring. And, three weeks in the primary fermentor is usually not enough time for off-flavors to occur.
From How To Brew
Ales are usually ready to bottle in 2-3 weeks when fermentation has completely finished. There should be few, if any, bubbles coming through the airlock. Although 2-3 weeks may seem like a long time to wait, the flavor won't improve by bottling any earlier. Some books recommend bottling after the bubbling stops or in about 1 week; this is usually bad advice. It is not uncommon for fermentation to stop after 3-4 days and begin again a few days later due to a temperature change. If the beer is bottled before fermentation is complete, the beer will become over-carbonated and the pressure may exceed the bottle strength. Exploding bottles are a disaster (and messy to boot).
So don't be in a hurry to rush the beer....give it the time it needs and you will infitley be rewarded with better beer.