These are made at different places in the mouth. Find the right place and the difference takes care of itself.
اAlif
The empty cavity
No contact at all. The air runs freely through the open mouth and throat, and the shape of the opening alone decides whether you hear a long ā, ū or ī.
عAin
The middle of the throat
Halfway up the throat. ʿAyn constricts it and lets the voice through; ḥāʾ narrows the same spot with no voice, a clear hot whisper.
Two words, one letter apart
Everything else in these words is identical. If you can hear which is which, you have the letter.
أَلَم
alam
pain
عَلَم
ʿalam
flag