Access includes any activities designed to make the convention available to persons with disabilities (PWD) who might otherwise not be able to attend or fully partake in the convention. Access is an important part of many areas of the convention, but its a good idea, even for small conventions, to have someone assigned to coordinate access and make sure that all convention attendees are as well accommodated as they can be.
In the United States, most facilities are required to meet standards set by the Americans with Disabilities Act. However, high load on elevators and long distances between function rooms can be a significant issue for PWDs.
Larger and/or more spread-out conventions often arrange for scooter rentals, generally by advance reservation and/or by referring attendees to a rental service, to make it possible for people to get back and forth between panel items over the course of the weekend. A 2000-person convention in a compact venue might need only one or two, whereas a Worldcon typically requires dozens of scooters due to the more spread-out facilities, less-mobile demographics, and longer (and thus more exhausting) duration of the con.
Seating (especially in the elevator lines) so that people with hidden disabilities can rest, reserved seating for wheelchair users who may not be able to make it from one panel to another as quickly as other attendees, and clear paths in convention areas such as the Con Suite are all useful accommodations. Some conventions use sign up sheets and priority seating so that people with disabilities do not need to wait in long lines to enter major events. (The sign-up sheets can be given to the people working the door of the event, letting only the people who have signed up bypass the line). If you have scooters and wheelchair users at you convention make sure that every panel room has at least one "parking space." a taped square, free of chairs. This space should not be in the back of the room. Optimally, there should be 1 parking space for every hundred seats. Like this, but... not in the back of the room.  Also, any platforms or stages you have, must include access ramps, so that panelists (or Hugo Honorees, or Masquerade participants) can participate as fully as any other attendee. Wheelchair-accessible shuttle buses may be more expensive and less accommodating than simply paying for taxis for PWDs, if accessible taxis are available in your area, as taxis are more able to provide door-to-door service than are buses.
The most common visual accommodations are for publications. These can be provided in Braille but not all visually impaired people read Braille. Screen readers are becoming popular. Some, but not all, PDF documents can easily be read by screen readers, and there are document formats particularly designed for this as well. Having access to the program guide, souvenir book, etc., a couple of weeks ahead of time allows for reformatting the docs with a sane deadline, and for making the docs available for download ahead of time. Large print versions of documents are easy to make, and there are special fonts such as APHont designed to make large-print documents easier to read. E-text can also be distributed at the convention on thumb drives, which can be loaned out from the info desk or registration, depending on the size of your convention.
Web sites with accommodation for the visually handicapped and hard of hearing can be published, if thought is given to incorporating the features in the site design. There are guidelines for this published by the World Wide Web Consortium (W3C) and others.
A descriptive map, in addition to visual maps can also be useful to people who are blind or have low-vision as well as other convention attendees.
Arisia conducts tactile tours of its Art Show and Masquerade, which are very popular.
For the hard of hearing, assistive listening devices are available which transmit over FM frequencies, and some attendees have receivers for these systems. In the Boston area, NESFA has two such systems available and sometimes lends them out. Text transcription systems are also available, and Arisia sometimes provides transcription using laptops connected to a chat server.
ASL interpretation can be had in most cities. It can be expensive to provide wide interpretation for extensive programming tracks, but if you publicize to the Deaf community that you will be offering it you may see an uptick in attendance as many such communities are starved for ASL-interpreted events to attend. If contact is made early, enough interpreters can be obtained and placed were they will be best used. Arisia has in the past arranged particular program items to interpret with members of the community.
A less expensive alternative might be text transcription interpretation, where a trained typist provides a running transcript of the spoken program, much like teletext/close captioning on television. This will involve more technology support, e.g. notebook computer(s) and display screen(s), but there will probably be more trained volunteers available to do the work.
Allergies and Sensitivities
Many people know have allergies and sensitivities, to foods, perfumes and/or cleaning products. You may wish to ask attendees to reduce use of perfumes at the event, and only allow food in certain parts of the convention. At large conventions, (more than 2500 people), attendees with ADD/ADHD, on the Autism spectrum, or with a susceptibility to headaches may benefit from a dedicated quiet space. At some conventions a reading room may suit the purpose, other conventions may wish to set up a Quiet Room.