Get a drum sander and an electric edge sander
You need to get a drum sander and an electric edge sander. These sanders can easily be found at your local home improvement or local rental stores. It is advisable for you to rent these tools. Keep in mind that a drum sander is larger in size. The sand paper moves back and forth in this sander. On the other hand an electric edge sander is smaller in size. It covers all areas which drum sander cannot reach.
Prepare the room
After getting the sander, you need to empty the room where you are sanding; clear out the whole room. For light fixtures, you can cover them with sheets or large rags. In addition to this, you should remove nails, or hammer in any nails which are out on surface.
Use the drum sander
Next you need to use the drum sander. However, you should take caution by wearing earplugs, mask and safety glasses while using the machine.
Sanding an uneven floor
In order to sand an uneven floor, you need to sand in the direction of the grain. First sand diagonally and start from a corner of the room. You need to sand towards the opposite corner.
After this, you need to turn the sander off and go back to the starting place. However, you are required to sand two inches to the right this time. Continue doing this and keep in mind that you will need to sand continuously in order to even the floor.
Sanding an even floor
In order to sand an even floor, you need to sand in the same direction of the grain. Sand in a similar way like you sand the uneven floor. You should start from one corner and move towards the other.