I'm giving the classical astrologers' take on this question.
Venus and Jupiter are the lesser and greater benefics. They both create benefit, Venus through pleasure and Jupiter through increase. Venus rules not only love, but beauty, marriage and sexual pleasure. She will show that which you desire and that which attracts you. You should look to the sexual nature primarily through her.
That being said, all planets have houses in which they are "joyful". The joy of Venus is the 5th house, the house of pleasure and amusements. In horary it is often used to represent romances, but it also represents games, amusements, entertainments and sensual delights. All of these things are also under the domain of Venus. Remember, Venus's domain is the bedroom. Mars' domain is the battlefield.
The 8th house is the house of death, other people's money, inheritances and the management of estates, and in my opinion should not be used for the sexual nature.
As far as the Moon is concerned, she, along with Venus, are called "appetitive" and represents our appetite and the thing we reach for in response to stimulus. Aspects of the Moon with Venus can make a person sexually inclined, as the Moon primarily responds in a Venusian manner. Of course, if Saturn is involved in the aspect he can put a damper on sexual responses.
I respectfully disagree with Mars being connected with desire. Venus represents desire and Mars representing our actions, or how we actually do the things we do, actually goes for the thing Venus desires. That being said, he is important for the "execution" of our sexual desires. If he is in Venusian signs (Taurus, Libra) with Venus in Martial signs (Aries, Scorpio...yes, Scorpio!), you can bet the person will have strong sexual nature, and may have problems keeping it in their pants.
In looking at many charts, I have also found that a profusion of water signs makes the person highly sexual. Remember that Pisces is the exaltation of Venus, and Scorpio rules the sexual organs. Generally, if the Moon is in a water sign and in trine to another planet, especially benefics Venus or Jupiter in water signs, the nature is generally highly sexual.
So
1. Check out Venus's position and aspects. Make sure she's not in Virgo which is her fall.
2. The fifth house and it's lord. Pleasure comes in all forms, so if Saturn is there or rules it, it could mean that they get pleasure out of work, isolation or ponderous activity.
3. Check the Moon, is she in a water sign? Contacting Venus? Contacting Venus or Jupiter in Water signs? In her exaltation of Taurus, which will make the native highly tactile and often sensual depending on the Moon's aspects.
4. Mars executes that which Venus desires. How he operates will show you the native's approach to sex and how active he is about getting it.
Hope this helps.