So you are on a chat room and looking for some of the best lines to use to chat up some of these horny grannies. This is nothing like chatting up real grannies in the real world; this is online. Ok, so the next thing to do is to put yourself in her situation, so imagine you were a horny granny, sitting on an online chat room and simply waiting for a man to woo you into bed, what would you want someone to say to you?
Telling them they are attractive and you are interested in meeting up for sex is easy, I mean, why would you be lying?
As for being serious, try explaining that you are deadly serious.
Ask her, if you did meet, where would she want to meet you? If it is a hotel, tell her you can book it that night if she is interested. If it is dogging, go to that dogging car park and send her an image to prove you go there regularly.
But these days, who says you have to be with each other to begin the sex talk.
Dirty chat is sometimes quite erotic over iphone or direct message.