Well, I suck at this stuff, but since the scoring is a mix between military score, economic score, amount of research, population amount, length of game and dificulty are there the following possibilities for higher scores.
-Military conquest gives the most. Reason: The more planets, the more population and money. And you get all planets if you win this way.
-Research everything before you win the game.
-Farms, farms, farms. Farms everywhere. Try to max each planets population cap.
-Build as much military ships as possible.
-Try to amass as much money as possible and have a high income. (Which is easy with lots of planets.)
-Win the game as fast as possible with as much things completed as described above.
-Play on gigantic galaxies with abundant everything (for as much planets and the highest pq planets possible).
Finishing games on suicidal with up to 5 Trillion people (annoying display bug btw.), thousends of att 300 def 300 battleships, everything researched, Quintillions of credits, etc. should give lots of credits.
