Whether you are lifting a load onto moving skates to move across a room, or you are lifting it on a sling, the load has to be secured in order to carry out the lift safely. This should be a point that is covered in the training of any members of staff, when they join the company or when you are refreshing their training.
If you are lifting a load in a lifting sling, it needs to be the right size of sling in order to hold the load and allow it to be secured effectively. You can then go about using anything else you might need to hold it in place, like netting or ratchet straps. These should also be used if you are transporting a load on a vehicle, to secure it down. If you are lifting a load by hand, make sure everyone is taking the weight equally and the load is safe.