I sometimes see “all ready” where “already” is required.

Problem:
“All ready” is an adjectival phrase whereas “already” is an adverb.

Explanation:
The adjectival phrase “all ready” means entirely ready.

For example, “He was all ready to leave for Argentina.” means “He was entirely ready to leave for Argentina.”

The adverb “already” means either previously or now or so soon.

For example, “He already had left for Argentina.” means “He previously had left for Argentina.”

And “He is already here in Argentina.” means “He is now here in Argentina.”.

Solution:
Use “all ready” when you mean entirely ready. Use “already” when you mean previously or now or so soon.