If it's a general meeting with a casting director, Fuzz, then they aren't looking for anything in particular - that is why it's a 'general meeting'. Or, to be less off-the-cuff about things, they are looking to basically meet you in person, learn a little about your background in acting, your past work, your present intentions, and what you consider working in the profession to mean to you.
Essentially, getting a general meeting (especially in this day and age) is a very good solid achievement because so many casting directors do not manage to see aspiring actors personally because there are so many demands on their time. That they are making the time to have a chat with you is a very good sign, and making the personal aquaintance of any casting director is very useful to your career. They have obviously been impressed/intrigued by whatever you have already shown them, and are interested to meet you in order to find out what kind of actor you are in person. They may ask you to cold read for them if they are in the mood, so be prepared for that possibility, or even to see you perform a speech you know well if you have one, but they are not holding an audition with you, so don't worry about aspects like that; they are meeting you with a view to having a face to face discussion with you as a person to see whether you would make a good, solid and trustworthy choice to put forward in the event that they find themselves casting something you are suitable for.
Other than that, be polite, be inquiring, try and find out about them as well as allowing them to find out about you, and then leave matters at that. That is all that can be expected from a general meeting, as there is no job offer immediately on the table (unless the casting director mentions otherwise, at any point). There may not be a job offer for the next year. It is possible that you will have to remind the casting director yourself of who you are the next time a job comes up that you know you would be suitable for, and you realise they are casting it! But the benefit of the meeting is to ensure that, if and when this type of thing does happen, you can contact the casting director concerned and remind them 'Don't you remember that great meeting we had a year ago? Would you be prepared to consider me for this part, which I felt I would be ideal for?', and you will speaking as a familiar figure, not an unknown quantity.
It is also worth remembering that being well in with casting directors is fantastic, because they hold open even more doors than an agent can towards getting you seen for prominent and well-paying work - but that, precisely because they work for producers/directors themselves, they cannot guarantee you jobs. They don't really have a say in whether you can land a job or not, which is something that remains between you and the director/producers of any production. What you should offer a casting director is a good option for casting - which means that they want to see you are passionate about your business, know your own career plans, have an interest and enthusiasm in the business in general, as well as other aspects of life, will be fun/professional/helpful to work with etc. Then, they can reliably put you forward for work on their behalf knowing you will do a good job for them, which is something that benefits both them and you.
Hope that helps
Lee.
