This is a practice I highly encourage. I grew up with this practice, though I fell out of it with time due to the toxic elements of the tradition in which I was raised. The prayer I currently use is a traditional Catholic prayer.
"Bless us, O Lord,
and these, Thy gifts,
which we are about to receive from Thy bounty.
In Christ's Name,
The Sign of the Cross is made prior to and after the prayer. According to some sources, the person reciting the prayer can make the Sign of the Cross over the food itself. I encourage all these practices.
Gratitude for one's food is something that shouldn't be overlooked, but it should also be genuine. There's no point in someone saying it if they don't genuinely have gratitude. That's a completely different life lesson one might learn at a different time, I think.
Grace before meals is a way to incorporate our spirituality into ordinary life and to infuse the food with the Divine energy, or at the very least, infuse our awareness with the remembrance that the food is already infused with Divine energy.
There are many daily rituals we can do, including Morning and Night Prayers. We'll talk about these in another entry.