For children with limited visual acuity, it is important to make sure you place the student desk near the front of the class where she has the best chance to make out what is one the board or objects you are holding up. For activities like watching videos or PowerPoint presentations, you might want to place the student even closer.
Just as with sight, there can be varying levels of impairment. A student might be totally deaf, in which case the school may provide a sign language translator. This person should be directly in front of the student where he can easily relay your lectures. The translator also needs to be positioned so he can see what you are doing. If the person is not fully deaf, then you might simply need to move her closer to the front. Keep in mind that a noisy classroom location can make it difficult for the hard of hearing, so you might want to find the quietest room the school has.
Students with mobility issues, such as those in wheelchairs, also may necessitate certain changes in the arraignment of the classroom. In their case, it will often be difficult for them to negotiate their way through the crowded aisle between desks. In this case, you should place the near the front. But you should also widen the aisles to the extent that you can. One way to do this is to take the desks from one row and place them at the front of the other rows. Also, provide spaces where students can keep their belongings so they don't end up blocking the aisles.
One challenge you will face in integrating students with disabilities into your classroom environment is getting the other students to understand the need to accommodate the needs of the disabled student. The key to a successful integration is preparation. With younger children, books and videos on the subject of acceptance of differences can help, while frank discussion are best with older students.