When we talk about "preparing for Thanksgiving," we usually mean buying the turkey, cutting up the bread for stuffing, and baking a pecan pie or a pumpkin pie (or both). Even though Thanksgiving is an American national holiday that doesn't exist in the Catholic calendar (though the Church does provide a special Mass to be celebrated on Thanksgiving Day in the United States), we should still take this opportunity to express our thanks to God for all of the blessings He has bestowed on us. And proper thanksgiving, just like a proper Thanksgiving, requires some preparation.
First, we should know what it means to offer thanks. Prayer of thanksgiving is one of the five major types of prayer, but it is perhaps the one most neglected. When things are going badly, we usually remember to ask God to make things better, but when things are going well, we tend to forget that God is the Source of all of our blessings.
Second, we should plan on making Thanksgiving the start of an attitude of thanksgiving that will last all year long. Pausing always--even when we're out in public, or just grabbing a Big Mac--to pray the Grace Before Meals is a very good start. Finishing with the Grace After Meals is even better, because it is written specifically as a prayer of thanksgiving.
If your family isn't in the habit of saying Grace After Meals, there's no better time to start than at Thanksgiving. (And, with its remembrance of the faithful departed, Grace After Meals is particularly appropriate during the Month of the Holy Souls in Purgatory.) Simply print this page to make a copy of Grace After Meals that you can distribute at Thanksgiving dinner. And be sure to make extra copies for your guests to take home with them!