The general rule of thumb is to apply only as much deck stain as the wood can absorb. Typically this will be 2 coats, unless you are dealing with extremely dense hardwoods which may only be able to absorb 1 coat of wood stain. Watch this video to see more tips on how many coats of stain to apply.
The number of coats will determine the final appearance of the wood. Essential and Extreme DEFY Semi-Transparent Wood Stains have a flat finish after one or two coats. But DEFY Ultra Semi-Transparent Wood Stains offer a luxurious satin finish after two coats, giving your outdoor wood the appearance of indoor wood.