First, you need to be really fluent in the language your deck "speaks." The conversations between you must be relatively easy, free-flowing, and reciprocal. This alone takes a while to develop. You should know what your deck means when certain elements present themselves. Do wands represent fire to you or air? Once you have determined the elemental associations with each suit, and understood the individual card meanings (for the most part) you might then be ready to experiment with timing.
The easiest method is to build the timeframe into the question itself. You ask the question in this way: "In the next week, what must I be focusing on in order to get my manuscript published?" That way, you've limited the timeframe to one week's time and any future or outcome cards in the spread will be predetermined to fit in that timeframe. Cheater. Actually, that's a great way to be very specific with your question, and the more specific you are with your question, the more specific an answer you will get. So that's one way. However, it occasionally leads to asking tarot again and again the same question only with different timeframes. How about in two weeks? Three? A month? If anything will get you chasing your tail in circles, asking the same question multiple times in a row will. You're asking for a headache.
There are many and varied methods tarot readers use to determine timing, but what I've found is that they're all dependent on that reader's own relationship and associations with the cards. For example, is fire or air faster to you? Since fire is associated with light (the sun), I view wands as the fastest suit. Swords is slightly slower, as a moving breeze. Cups I associate with water, hence a bit slower than air, like water moving in a stream. Pentacles represent earth which moves very slowly. So these elemental associations with the suits give me clues as to the speed of the event in question. Another clue comes from the numbers on the cards. One (the Magician) and Aces are very quick, almost instantaneous. However, with the Aces, one has to consider the element of the suit as well, as an Ace of Wands will be much faster occuring than the Ace of Pentacles. Fours, on the other hand, the number of The Emperor, are rather static and solid, not going anywhere anytime soon, stubborn almost. So even a Four of Wands, while not as rooted as a Four of Pentacles, is very easygoing and will wait a while. Yet another clue comes from whether the card is a Major or Minor Arcana. The Majors, being "destiny" cards, meaning events that have a major impact on your life, seem to indicate something already in the works. It's going to happen. However, the actual meanings associated with the card must come into play here as well. Temperance, for example, though a Major, takes a while to find just the right mixture between things, and is indicative of patience. We wouldn't need patience if the thing we want to happen comes quickly, so this card says it's going to take a while. It will happen, but not so fast.
Suits can also be associated with seasons. Again, different readers have different associations, and some of these systems are based on the astrological associations of the cards (which is a whole realm in itself!). One of the problems with this system is, again, different people have different astrological associations to different cards. So if you use this system, find one set of associations and stick with it. The key seems to be getting one system embedded into your subconscious so your interaction with the cards bring up those associations more naturally. For me, personally, Swords (air) represent winter, Cups (water) represent spring, Wands (fire) represent summer, and Pentacles (earth) represent autumn.
The numbers on the cards can indicate the number of days, weeks, or months. Or the number of the month, such as 9 being the ninth month, or September. The tricky part is figuring that out. Some people associate pentacles with months, so the Nine of Pentacles then would mean either in 9 months or September. Also, readers sometimes simply pick up cues from the images on the cards themselves, noticing whether the scene in question looks like it's occuring in summer or winter or on a particular holiday.
Combining all these clues and systems and tossing in a healthy dose of intuition and knowing your particular deck's idiosynchracies based on many, many readings and grasping at something so intangible as the sands of Time itself, you still may find you can only come up with a general sense to answer that elusive question: "When?" In my next post, I'll share a wonderful spread a friend of mine developed that is designed specifically to answer that question, but we've found even after using this spread extensively, you still need to figure out your own system and even then it's pretty trial-and-error. There have been times it's been so eerily accurate that it's made us marvel, but other times she and I will bemoan, "Why did Tarot lie? Why does it lie like that?"