When you have a planet in any house of the chart, its position is more important than its rulership, but the second is also essential. Lets see why.
If I have Mars in the seventh house, there is some friction awaited in marriage or partnerships, but if this same mars rules good houses of the figure, the action gets better qualities than it would be with bad houses (6, 8 and 12).
The so-called benefics (venus and Jupiter) portends bad events when rulling bad houses. I had an interview with a woman who have venus in her seventh house, ruling the 12th. I said to her her partner hid some secret from her.
When I analised venus’ dispositor, Júpiter, its position in the second house told to me the secret involved money. And so was that, as the woman said!
It is very important the analisis of the rulership of a planet. Its like an qualifier of the planets actions. If the planet rules the fifth house, it brings pleasure to every house he is in. The eight brings death and misfortune, and so on, as the 12th too. Astrology gets less enigmatic when analising the rulerships! Mars in the fourth house, for example, is not a real problem if he rules the fifth. You can make a lot of physical exercises at home!