Good question. I've stickied it for reference.
Yes or No can be a problematic way to approach horary because questions are usually more complicated than that. We change our thoughts as we get closer to a reality and that affects the way things go and what we want.
You might ask, 'Will I get sick?' and there could be a trine between the ruler to the Asc and the 6th house (health) and the Moon's last aspect a parallel to Jupiter and you'd say No! You're going to be healthy! But what if getting sick means you don't have to go on the trip with your friend that you unconsciously have been fretting about? What if getting sick means a week off work that you really need? The trine between your ruler and Health could me YES! You get that week off and you will be well looked after, catch up on reading, meet a gorgeous doctor and have a wonderful time.
You can see that the intention behind the question becomes most important.
More than that, if you can imagine it, you can have it, so as your consciousness develops these yes or no answers become, 'do you want it?'
I think Horary can tell you a lot about what's going on beneath the question--why you asked it, what it means to you, what you really want. Ultimately Yes or No is entirely up to you. You decide! Because getting in touch with your feelings about the query can help, the horary may be viewed as a map of the terrain. Most important to ask is
1) What do I want? and
2) Why do I want it?With that prologue, here are some basic rules that can help.
First, the chart must be readable. 1) Less than 3 degrees (if less it is
too soon to ask)
2) More than 27 degrees rising (if more it is
too late to ask)
3) Moon not Void of course by zodiac or declination (a void moon means 'nothing will happen' or 'there is nothing to worry about). Remember, the moon is allowed all applying aspects before she changes signs.
7) Saturn not in the 7th (this rule doesn't apply if the astrology is asking about themselves)
If the chart is radical and fit to read unravel your question by looking at the rulers:
1) Check the aspects between the rulers in question (the Asc. ruler, the co-ruler Moon and the ruler of the 'other's' house or the situation's house) Look at the LAST aspect made within the sign and it says a lot about how things are going.
Trines almost always mean a positive answer; (again, consider the introduction)
squares are limiting beliefs getting in the way, or what you say you want isn't what you
really want.
Oppositions can mean you give up on it before the end, or there is separation - detachment, again, not what you really want.
Sextiles usually mean cooperation and the
inconjuncts, 30 and 150 degree, often mean a 3rd party gets involved.
Conjunctions mean it's already there! You've got it!
2) Rulers that are retrograde, combust the sun, on a fixed star etc indicate the person/thing is working at cross purpose, or under par. They don't know what they want or they are fighting against what they don't want. (making it stronger)
3) Look at the rulers first to give you a grounding in the question and then watch how the moon unfolds. What aspects she makes tells you more about where things are headed at this point.
Obviously a traditional horary astrologer would answer this question differently--read William Lilly for trad view on this topic!
Anyone else have insights here?
Thanks for the question,
Kim
Good question. I've stickied it for reference. 
