Use good french bread or any textured bread; do not use "Wonder bread" type, and even Texas toast is not as good- though better than wonder. For the best, cut thick (about 1") slices of bread and let them stale (not rock hard, just so they're nice and dry), then give them time to soak up your custard base. If this is too time consuming, thinner slices of solid bread work well with a quicker soak and a slightly hotter grill.

Speaking of the soak, the biggest mistake people make with French toast is just dipping it in the batter without letting it soak.

No salt. Grill in butter that has enough salt for the toast, lightly dust with powdered sugar, (or toppings).

Equal amounts of eggs and milk (use less milk for a more custardy inner texture), whatever spice and flavor you want, then onto the griddle. But you have to give the "custard" time to cook. So the griddle can't be to hot- you don't want burn the outside before the inside is done to a custard like consistency.

Here is a food service recipe for 48 servings with frou frou toppings;

Berry Good French Toast (Rich's)
Yield 48 servings
Ingredients

3 large loaves French or Italian Bread
1 quart whole milk or half and half
4 1/2 cups Eggs (that's about 2 dozen)
2/3 cups Sugar
4 tsp Vanilla Extract
1 Tbsp Rum-Flavored Extract
1 tsp Nutmeg
Powdered Sugar, as needed, 1 pound
6 lbs Frozen Strawberries, thawed, drained, and sliced
48 oz On Top® Whipped Topping (PC 02559)
Directions

Bake bread, following directions on case. Let cool, then slice 16 slices out of each loaf.
Arrange bread slices in single layer in 2 greased full sheet pans (18"x26"x1"). Set aside.
Combine Rich's® Whip Topping®, eggs, sugar, vanilla, rum extract, and nutmeg until well blended. Pour mixture evenly over bread slices. Turn bread slices over once to coat both sides. Cover and chill overnight.
Remove from refrigerator. Let stand for 30 minutes at room temperature.