Clear out your basement:
By clearing out your basement you will get a good idea on the amount of space that you have available to make your fallout shelter. Put things away in boxes and store them somewhere else to open up some space in your basement.
Develop floor plan:
Most basements are not that big and you will have to develop a proper floor plan to utilise the space effectively. Decide where you might want to put up walls and partitions inside your basement. Also, be sure to plan for bathroom and sleeping facilities as well.
In order to make your fallout shelter strong, be sure to reinforce the walls with concrete. You will want to add some strength and thickness to all exposed surfaces in your basement.
Be sure to reinforce the entry of your basement using a combination of steel and concrete. This will ensure that the doorway is strong and will provide some protection.
If you want to stay for extended periods in your fallout shelter you will need a steady supply of clean air. Buy an air filtration device specifically designed for fallout shelters. Some of these units take carbon dioxide and make oxygen through the use of special filters and attachments.
All humans require water in order to survive. Try to dig your own deep water well and pipe this water supply to your basement fallout shelter. Be sure to reinforce all of the pipes and water fixtures.
Electricity and fuel:
Buy a large backup generator that you can use for electricity when you are in your fallout shelter. Also, be sure to store an ample amount of fuel as well. You might want to look into possible solar panel options as well.
Food and medical supplies:
Be sure to have an ample supply of food. Buy and store dehydrated or freeze dried foods that have a long shelf life. Also, put together a complete medical kit which you can use in case of an emergency.