One of THE most important yet overlooked key to success in playing the cello is correctly shaped chair with seat at the proper height FOR YOUR BODY. Everyone is told you need to sit up near the edge of the seat but choosing a chair with a flat seat (most angle downward toward the back) will help you stay in the correct position and keep you much more comfortable while playing.
Also, while the end pin is a great tool for adjusting the cello’s position (relative to the floor), if the chair’s height doesn’t allow you to sit correctly with your feet flat on the floor you may consider a chair with an adjustable seat height. If you have particularly long or short legs, it will make all the difference in the world. There are high quality adjustable height chair for under $100.