How do you get entry's data from Ajax form submission with Guest plugin?
According to the README, the Guest Entries plugin accepts an AJAX request, and returns an object containing the entry ID, title, and so forth.

As such, if you're using jQuery, you should be able to do something like this (not tested):

$.ajax({
    data: $('#theform').serialize(),
    method: 'POST',
    done: function (data) {
        // The entry title.
        console.log(data.title);
    }
});


I'm not sure how Guest Entries handles errors, so you'll probably want to check the data.success property, before proceeding.