How to go for the kiss?

this has happened to me the past few dates where i take the girl out, we have a good time and it get to the point where we are on the doorstep but the girl wont stop talking. she wont shutup about her new cat or something her friend did and its hard to set the mood for a goodnight kiss. are they just nervous? shy? dont want a kiss? we stand there for forever just talking about stuff which is nice but what does it mean and what do i do about it?