Take the btc paper, and give to read. Some times could be the best answer to all doubts.

"If you don't understand how it works doesn't mean it doesn't work!"

Something like this, but stop joking
Make a brief summary of what you think btc could improve...
like "privacy", "banking system" and so on... I think every one of us noted a peculiarity on btc itself and know what can make the difference, and could help the "common user