Look as far down the runway as you can. This will improve depth perception.
To try & get the correct 'picture' in your mind, get in the habit of having a look down the far end of the runway as you line up for take off. This will show you what the picture out the window will look like when the aircraft is on the runway. (a bit different from touch down due to the nose high attitude, but close enough).
Then get your eyes down the end of the runway during the flare when the skipper is doing the landing. Decide from the picture you are seeing if he/she is going to roll it on, bang it on, or float. Then see what actually happens & mentally adjust your picture.
Finally, always remember that when it comes to nice landings, you will 'win' a few & 'lose' a lot!