Well, if you believe in that sort of thing, they actually feed off the person's life force THROUGH the sexual act - often until the victim dies.
As to what attracts them... I don't know right of the top of my head.
UPDATE: In my handy-dandy The New Encyclopedia of the Occult by John Michael Greer (an excellent book by the way) it says in part:
Succubus (Latin, "one who lies under") In Western demonology, a spirit that seeks to have sexual relations with men. Monks, priest, and other men committed to the celibate life were believed to be particularly at risk from succubi.
So how `bout that?

Careful though, some succubi have hidden blades in there. You know what I mean. But they're only found in the middle east so I wouldn't worry about it.

I think the come after people who over indulge

It's impossible to contact them without them finding you. These are often glorified creatures, the only things really special about them is that they're immortal and they can't reproduce. they also have incredibly good powers of seduction, but it's unknown whether that's a product of their powers, or whether it's just an eternity of experience. they pretty much practice hedonism in the most primal(and awesome) form, and just have sex with anyone they feel like seducing. so pretty much the awesomest thing to be, ever.

I've been involved with two Succubus for over 30 years, this is not a gag.
These spirits come to you by one of two ways. Either they pick you or summoned by ritual.
I do not suggest ritual. It is dangerous in many ways and you can't be sure what might come through. I will not provide any information regarding rituals.
If someone is paticularly sensitive to spirits and think about them, chances are better about attracting the attention of one but nobody knows for sure what attracts one person over another.
I'm part of an online community of others experiencing the same things and is more widespread than you know.
Some information:
1. They do have all the "parts" of humans.
2. These parts are "Supercharged" for pleasure
3. They are whitty and smarter than we are.
4. They don't drain energy. Just opposite.
5. They have 1 thing on their mind and it isn't mischief.
6. They have a wide range of personalities just as humans.
7. Interaction is when wide awake, not sleeping.
8. They can look like, sound and feel like anything or anyone.
9. Humans never "finish" while interacting with them. It's more a "Liquid bath of intimate love and extacy".
See my profile for more information.

Sergeant, how do you view your profile? I would very much like to view some of the stories contained within your community.

i have no idea, i reckon a spell or they just feel drawn to you.
..i don't know why people fear them i think they could be sorta nice if you give them a chance rather than be terrified.

for a more extense answer, where can I find the ritual part to contact one of these entites,I.E. succbus... doyou know, or will you name a book or two on the subject?

I believe I've experiened an Incubus, though only twice. I came to find that it would come to me on the 14th of the month. The first time it happened was Valentine's Day (February 14th) and again on March 14th, each late at night, near midnight. I somewhat awaited it Saturday (April 14th) but it never came, though I didn't expect it to. I was just wondering, since the channel has already been opened (in a sense), is there any way to call him back? A lot of people say that Incubi and Succubi are dangerous, but I can say without a doubt, that's a bunch of malarky. Perhaps to some they can be quite aggressive, but respect goes a long way. I've crossed paths with countless Demons, and each time I've given them my respect and came out just fine. Hell, I've even rebuked one from my home (he was harming my fiance and began trying to harm me) and I felt his anger until I told him I meant no disrespect and he calmly left afterward. It just depends on how you approach these beings. What you give, they give. Simple as that.

So is there such as these things, i just finished watching "Paranormal Entity" I thought it was based on a true story, but when I saw the professor talk I wanted to find out if it was real, I'm scared it might come to me, I belive in God, but I;m still scared, I'm only 15 years old. So can someone tell me the 100% if these Incubus are real or not, I mean its stupid...demons if thats even normal for demons to be alivee?

anyone got any ideas on how to attract an incubus without doing any rituals, like attracting them with certain stuff around the house.

I'd like to say I may have fallen in love with 1 specific one came to me 5 times on different weeks this one did me no harm simply in my dream all we did was try and reach out to each other (so to speak) I knew what she was cause I had never seen her in my life before 5 times man and all I did was save her from danger , what in the hell is that supposed to mean? What am I to her I asked no answer of course but all in all its the same run is all she says but I refuse then I wake up . Run from her? Or something else? Felt so real I woke up with tears and a wet shirt like I ran a mile , intense experiance . I thought I had gonne mad . Now I have not seen her in a long time and dare to say I miss her cause every time I'm near her its pure happiness. Call me crazy don't matter I know what I saw lol XD

Hey I have a qestion how do I make my icubuse attracted to me and the resin I ask is be cuse I want to give back a lil to him he's alway be good about puttin me in the mood and I want to try it on him can I get some tips plese

I got freaked out two nights ago that some thing was lying next to me it was really creepy because when irolled over I seen one