There are a few things that you will need to do in order to prepare for a professional carpet cleaning. If you can move everything out of the room it would be better but if your planning to stay they it might be subjected to just straighten up the area, move out smaller moveable items, and then clean up with your vacuum.
First, straighten up the area or room that you plan to get cleaned. Things should be in order. Pick up things that might be laying around like blankets or shoes. Put them away where it will not disturb the area to clean. 
Second, move out smaller items from the area. If you have a small bookshelf, side tables, or lamps in this room, you might want to move it out of the area or room for the day. It is less for the professional carpet cleaners to work around. Less items on the floor will also help with the drying process and there will not be something over it to stop air flow to that area.
Third, do a quick vacuum around the area or room that will be professionally cleaned. This may seem redundant, but if there is dust or dirt that could have been picked up before hand it will make the cleaning process easier. This way it will help the process not wash extra grime in to and out of your carpets.
You may also purchase furniture slides to protect the feet of the furniture. It will be easier for the professional carpet cleaning to be done under heavy items in the cleaners can move your furniture easier.
To make sure you are prepared for the professional carpet cleaning you will need to straighten up the room or area, move out the smaller items, and vacuum up the area.
