Find Your Power Position
A common mistake many conventional or trap bar deadlifters make is setting up with their feet too wide. This has a couple of deleterious effects. If the feet are too wide, then the knees have nowhere to go but in. This isn't a good position to deadlift from. If the knees are in valgus, then "active foot" can't be attained.
Bad Position: Knees Caving In
Setting up too wide also has a cascade effect on hand positioning (too wide) and back positioning (too rounded).
Bad Position: Feet Too Wide
To fix this, imagine jumping as high as you can. Where would your feet start from? That's the power position.
Power Position: Feet More Narrow