Navigation to me is a game of crossword or Sudoku where you are given a portion of the answer and must fill in the blanks to get the complete picture. Like these games, navigation involves taking input from your surroundings and making it fit to the information on the map and making sound decisions based on that limited information......and like crosswords, the more pieces you have, the easier it becomes.
Distance is only one part of the puzzle. Pace counting to find the right reentrant will work but determining how large the feature is in the first place by looking at the contour lines would be faster.
I've struggled with this in past AR and I agree that determining what will and won't show up on a USGS map takes a little practice. I suggest that you carry a map on every run, even if you know your route like the back of your hand. Look at the features in the same scale of your upcoming race and visualize the terrain before your run. This reinforces the scale of features and distance.
There are too many pieces of the puzzle to list and explain here. Maybe others could take one aspect and expound a little. I'm sure it is already out there on one blog or another. Drop a few links. I like Spike's at:
http://okansas.blogspot.com/ His go back to March of 2002. Others could point you to hundreds more.
I still have a huge amount to learn about orienteering but I can say this for sure, you MUST force yourself to practice navigation to see improvement. Practicing your nav is just as important as hitting the roads and rivers for the athletic training. Every time you work through an interesting nav problem, maintain your location on your map while on the run or even make a decision poorly based on too little information, you reinforce and improve your own navigation techniques.
I can look back at past races and meets and easily point to incidents where I missed or ignored pertinent information. I have to ask myself if it was a lack of focus or was it a lack of training to focus. Focus and sound decision making are both elements that must be practiced for perfection in sport.