It really depends on what type of photographer / studio it is. Photographers should be pretty understanding that you're just starting out but a certain level of professionalism will be expected. As long as you have 12-15 images neatly organized in a uniform presentation (a zippered portfolio case with clear pages is fine) you'll be good-to-go. Try to pick images related to the kind of work the photographer does. If it's a portrait studio then don't show all food photography, in other words. Also study the photographers work / website in advance to try and gauge what they might respond to.

Feel free to bring along some extra images but don't offer them unless the photographer asks for more. Good luck! Let us know how it goes...