I disagree with this statement. It does take an expendature of energy to stay near the front, and some mental alertness. However this is far outweighed by not having to deal with the accordion in the pack out of every turn, having to bridge gaps in the Field, ect. Skills that will help this:

1. Learn to read the dynamics occuring in the top 10 or 20 riders in a pack. The movement here tends to stay the same race to race. It is possible to stay in the top 10 in a field and never really be at the front.This takes experience, but if you are at the back you can't gain it. If you find yourself towards the back of the field early on I would do everything short of blowing up to get to the front, in the long run you are much better off being a little gassed in the top 10 than bouncing aroung in the back.
2. Work on the ability to Jump then recover. You will need this to accelerate into small gaps/holes to help you maintain position.
3. Learn to Corner Fast, this is the easiest way to gain position w/o acceleration.