Before taking a job, you should read the job description carefully as you might be required to load and unload shipment. If you are working in an industry that has something to do with liquids, you might have to fill and drain out the containers. Apart from that, you might also be required to operate machinery and lifts for moving goods.
You do not need firm grip on advance math but your basic math should be of reasonable level. They will want you to calculate and keep record of the inventory. At the time of unloading shipment, some firms required their freight handlers to record the physical condition of the goods.
You should be physically fit as you might have to move goods by your hands. In case of small or medium sized products, stock movers often have to carry them from one shelf to another.
There are some cases where employers train their employees if there is some technical equipment involved. If you are to carry goods from one location to another, you must have a driving license.
You must obtain a diploma from high school otherwise you might face troubles in finding a job.
Note that your background should be clean as employers often run a criminal background check on potential candidates.