I have looked everywhere and I can't find a good answer. I have some custom objects with standard lookup fields on them. The users are wanting those lookup fields to be able to select multiple records in the object they are looking up to. I know the functionality is there, because you can do this on the user lookup object, but not in the custom objects. 

Can someone PLEASE tell me how I can create a lookup field that will allow the user to select multiple records from the object that lookup field is looking up to?