all ready / already
Fully prepared versus by this time.
All ready means that every member of a group, or the whole of something, is prepared: The files are all ready. Already is an adverb of time meaning by now or by a stated time, and it carries no sense of readiness: The files have already gone out.
Examples
Use The volunteers were all ready, with name tags on and clipboards in hand.
Use The movers had already loaded the piano when we arrived.
Avoid The movers had all ready loaded the piano when we arrived. (All ready is the error: the sentence means “by that time,” not “prepared.” Write The movers had already loaded the piano when we arrived.)