The blessing said at the table, and why it is said out loud.
Bless us, O Lord, and these thy gifts, which we are about to receive from thy bounty, through Christ our Lord. Amen.
A grace after meals exists too: we give thee thanks for all thy benefits, almighty God, who livest and reignest forever.
Say it aloud with guests present. It is the least awkward evangelization available to a household.
Every meal is received, not produced. Grace is the daily admission that the food, the work that bought it, and the people at the table are all gifts.
Jewish table blessing is the direct ancestor, and Christ blesses and gives thanks at every meal recorded in the Gospels, including the Last Supper.
The Latin form used in most Catholic homes comes from the Roman ritual and has been essentially unchanged for centuries.
Free, and the easiest habit on this list to begin tonight.