Major phases and strategies

OGame is all about resource optimization. The first resources to be optimized are metal, crystal, and energy, later deuterium and ships come into play. The first thing I've noticed is that the game takes a sharp turn from a metal constrained system to a highly crystal constrained system at about the point you begin research for the cruiser. I break the early game into two stages, starting to the first ship, and then, getting the early research done to support battle ship production. Mid game runs from battleship production to death star production, and the stasis is after you have death stars.
In the early game, if you are following the inactive raid strategy you normally have more than enough metal, but are short of energy and crystal (or have a risky energy system based on solar satellites). Building your mines to 15 and synth to 9 and powering it with solar panels requires 235,000 metal and 94,000 crystal. So the general strategy to that point is to lag development of crystal mines by 2-4 levels (and deut synths by 6+).

As a potential improvement to this, I've been playing with reducing the utilization of my metal mines and using the excess power to supply my improving crystal mines and deuterium mines from about level 15. Unless there appear to be lots of juicy targets early, in early galaxies, investing in mines is vastly better than spending to get enough deuterium for that first small cargo. It requires 3000, which means a major diversion of resources from the metal mines and much slower growth. As the galaxies become more active, there are fewer early inactive players and more people trying to raid them so your large investment in a ship, doesn't pay. In Uni 40 it has been much easier to climb the ranks with mines than the ship had been. Too many people are raiding the few weak planets not in new player protection by the time you have the points neccessary to get a ship.