I don't know how well this thread will do, but I do hope that some of the more experienced players will post some of their secrets here.
�nothing is more difficult than the art of maneuvering for advantageous positions.�- Sun Tzu �The art of war�
This was true in Sun Tzu's time and it is still true today. The practicality when a game is first started most players focus on colonizing as rapidly and as far out as they can. Thus they gain control of more territory, discover more ruins, and have access to better planets while providing a buffer zone around there home system.
"A military operation involves deception. Even though you are competent, appear to be incompetent. Though effective, appear to be ineffective."- Sun-tzu, The Art of War
Basically put concentrate on your game, and role play.
"Invincibility lies in the defense; the possibility of victory in the Attack." - Sun-tzu, The Art of War
If you do not protect your planets with mines, satellites, and weapon platforms, then expect to loose them. If you have the advantage, either in ships, technology, or resource production use it or loose it.
"One who sets the entire army in motion to chase an advantage will not attain it." - Sun-tzu, The Art of War
Look at the big picture and consider your options, if you focus your fleet chasing one ship, your opponant gains the advantage and can attack your systems while your fleet is off chasing its prey.
"Know your enemy and know yourself and you can fight a hundred battles without disaster." - Sun-tzu, The Art of War
I think that this is why the TOP players are the TOP players.