Should we follow the direction a planet rules or its position in the chart, for example an exalted Sun sitting in the West?
Follow the direction the planet rules: if the Sun is exalted, select the East even though it sits in the West of the chart. Also see where most benefic planets sit; two, three or even four directions can be favourable for one person.
Related questions
For someone with no astrology background, what does an exalted or debilitated planet mean in practice?
Learn the twelve rashis in order and the rest is simple. If the Sun is written with rashi 1, it is exalted, very powerful, and blesses the house and direction it occupies. If the Sun sits with rashi 7, it is debilitated and very weak; if that falls in the 4th house (North), building a house in that direction ruins the person. Vastu without this is incomplete, which is why even a perfect East-facing house can fail.
How far does the influence of a devta reach beyond its own pad?
As in a kundli, where Jupiter blesses whatever it aspects with full drishti, a devta also aspects the devta opposite it; Surya, for example, balances Varun. If you cannot balance a devta directly, balance the devta whose full drishti falls on it, and its gaze will set it right.
If the Sun is debilitated, can a Sun picture be kept in the East?
No, do not keep it and do not take on the trouble. Strengthen the West instead; its power reaches the East on its own.
The 5th lord is Mars but the child studies in the West. Is that wrong?
See in which direction the 5th lord sits. If it sits in the West, that is excellent; if in the East, choose the East. The East and North are best for study anyway, and if the lord sits in the South, studying in the South also works.
The kundli chart was shown with directions. How are those directions used, and what can a kundli tell about a house?
Go by the houses, not the numbers written in them: the top house is the 1st house (East) and the 4th house is North. If the planets on the North side are strong, the North direction is very good for the person. A kundli can even reveal where a person's house is, where its door is, how many windows it has and where a nearby river, pond or temple lies, so a map of the house can be drawn without seeing it.
A client has an exalted Saturn and a debilitated Venus. Can the bedroom be made in the West?
Yes, it will be very good. With an exalted Saturn, make the bedroom in the West without hesitation; WSW or even SW can also be used, but when Saturn is exalted the West gives the best results.