I just feel that there is no such a mainstream tactic for every game. Player needs to observe on the planetary system to choose the proper tactics. How about the landing zones? It is rich or poor? How far to the enemy landing zone? How large is the planet? Can enemy rush me? Is it a system which contains multiple planets? Does the system contain the gas giant? Does the system contain the planetary weapons? Should I rush orbital factory? There are just too many factors, so I believe there is no general opening tactic.