1) Be their customer and offer them payment with Bitcoin. Make them curious.

2) Call it Bitcoin - they don't need to know terms like lightning, on-chain until they need it or other unnecessary technicalities. Say "it's easy, you just need to intall an app".

3)Make them install Phoenix Wallet and backup the seed properly. Explain why it's important to not lose the seed.

4)At the start send them large lightning transaction so that the app opens a chunky channel. Make tham send most of the money back - that way they will be left with inbound liquidity. This step is also an excercise for them to try receiving and sending.