And, I prefer the verb 'help' than 'teach'.

i will teach him or her some basic sentences easy ones to encourge him later letters and formation of sentence and question

I will teach him first pronunciation and then simple sentences used in daily life and then grammar.

I would start from basic. Like in English people start from ABC letters if he is not aware of.

for arabic , i will start with pronouncement of letters , because there is some of letters in arabic that may sound strange for english native speakers , then basic vocabulary and verbs , and some daily expressions.