I'm having a problem with all my tile falling off the ceiling and I don't know what to do because I'm not able to hire someone to do the job. Does anyone know what I can nail up there to keep them from falling?
It depends on the type of ceiling tile and the type of ceiling, really. You could use anything from ceiling clips to ceiling adhesive, all available at places like Home Depot or Amazon.com
I believe you are probably talking about the 12 x 12 ceiling tiles that have been used in older homes and offices. You most likely have some sort of "runner" that hold the tiles in place and if these runners are falling it will be very difficult to repair.
The danger may be that if these are very old tiles (like 1980's) they probably contain asbestos and this may be dangerous for you to mess with as asbestos beaks up and is very bad for you to breath.
I do not know your financial situation but this is probably something you need to have a professional look at.
At least get an estimate of the cost to repair it or remove it so you will know what you are dealing with.
If you have low income, receive government assistance (foodstamps), or you are a senior or have disabilities you may be able to get some government assistance with repairs.
Depending on the material used for your ceiling and the cause of the crack, there are some ways the homeowner can temporarily or permanently repair a crack themselves. This is a page about fixing a cracked ceiling.