I just purchased a house in whiterun and had 3 questions... 1) lydia seems to be located in my house whenever i send her off... if i get married while she still stay in the house??? 2) Who can i marry or are there no limits to who you can marry... and finally, 3) How do you marry someone... thank you ahead of time =)

bump

cmon guys can someone just lend a helping hand??or sentence in this case lol??

There are only certain NPC's you can marry to my understanding but it's not something I've looked into in the game, but I did find it with a google search, you need an amulet to open the dialogue up.

Here is a http://www.uesp.net/wiki/Skyrim:Marriage to get you started.

I can’t confirm what Lydia does after you marry.

They are supposed to go to wherever you designate as home. With Lydia, who knows. She seems compelled to sit in that chair in your bedroom in Whiterun no matter what's going on.

I did experiment (with the console commands) by marrying Jarl Laila Law-Giver and she did in fact relocate to my house in Riften. But she kept going back to the Jarl's keep to sit in her chair or to wander around the cemetery. Lady is unhinged.

I can confirm Lydia still stays in your house after marriage. Giggity

LOL. Now we know why that chair is in the bedroom.

lydias your housecarl so whenever u parts ways she loyally awaits u at home...u could kill her if u want to part ways permanently

Okay first off, you bumped your post 40 minutes after posting it? C'mon...
And you were posting for someone to hurry up and help you before it had even been up for an hour? C'mon again...

To answer your question, Lydia is just a Housecarl. They are just basically like protectors of your house. Since nothing ever tries to hurt you or steal from you in your house, they really don't do anything except if you recruit them as a companion. There is one for every house. They aren't related to marriage in any way (other than that it is possible to marry most, if not all of them).
There are many NPCs in the game that can be married, but not all of them can. To do it, you need to go to the temple of Mara in Riften, and get an Amulet of Mara. Then, while wearing it, just talk to someone you want to marry. If they are available for marriage there will be extra dialogue options. In most cases, you have to do something for them, like a quest related to them or a small favor in order to gain their favor. That's pretty much it.