For school stuff, I sent in a check list that I made inside a sheet protector. It contained things like bring water bottle, bring lunch pack, bring homework sheets, bring text book for tomorrow's test etc. DS was supposed to check off each item using a dry erase marker before leaving for home. It worked for him and after 2 months of this, he did not need the checklist anymore.

At home, we remind, remind and remind and it helps somewhat.