These may be helpful to someone starting out. They don't provide an advantage over your enemy, but they will help navigate and manage your empire.
Empty Construction ListEdit
If you bring up the list of planets, you can quickly see what each planet is constructing in both the social and military queues. Use this to quickly find open planets not building anything.
Where is that minor race?Edit
When contacted by a minor race but you don't know where it is, look for a foreign planet with the name of the minor race. That is most likely their home planet or one in the system.
When upgrading a unit, you can upgrade all of the same type simultaneously. In the upper left corner, there is a checkbox to apply the upgrade to all units. Just make sure you can afford it!
Use the Mini map to expediate many tasks. Turn off all object filters to see resources. Use the population mode to find where to send freighters. Turn off territory filters to see where you haven't explored.
Moons and RingsEdit
As mentioned under Planet, moons and rings grant extra bonuses to planets, so keep an eye out for them.
Keep your population growingEdit
Planets at max population will not generate any more citizens. If you think you will ever be at war, create transports, put some population on them, and have them fly to a safe part of your territory. That way, should war break out, you already have a fleet of filled transports ready to go.
These are methods to take advantage of game mechanics or the AI to attempt to give yourself an edge over them.
Influence Trade AbuseEdit
Take a small planet heavily under your influence, reduce its population (via transports) and replace farms and embassies with other buildings. Now, trade that planet for a high price to another civilization with low loyalty. Within some time, the planet will most likely flip back to you. Repeat to gain more goodies from trade.
In the early game, build an economy starbase in the middle of enemy territory when at peace. Put every weapon and defense you can on it. When you declare war, the enemy will send fleets out to destroy the starbase. If the defenses are sufficient, it should be able to destroy quite a few foes before being taken down, thinning the fleet for your warships. Other types of starbases may be used, but economy cause the least distress.
Create fleets of constructors. During war, use them to quickly create and upgrade overlapping military starbases, affecting an enemy's strongest planet. Their bonuses will allow you to use small, cheap ships to deal significant damage. This is best done after choosing the evil alignment to keep costs down.
Even without espionage, you can deduce an enemy's tech list by opening up the Trade window. The differences in what you have and what they have appear as trade items. Now, using that, find a race that has a tech that most others don't. Buy it from them, then proceed to sell it to the others. You'll come out with the tech and a good deal of money.
In war, you'll often notice how enemy war ships will lock onto a particular target and chase it until it reaches it. The AI tends to build slow, powerful ships, so if you focus on fast ships, you can use them to lure away many of the enemy fleets while your more powerful ships focus on planetary conquest.
When you upgrade a ship, its HP drops to one but then maximizes when the upgrade is complete. You can upgrade a heavily damaged ship, and within a turn, it will be good as new.
Overlapping Trade RoutesEdit
You can create multiple trade routes from Planet A to Planet B. Using this, you can optimize your economy starbases to increase the trade on this one route and have it multiply its effect across your entire trade fleet. However, this does come at the risk if you end up at war with the owner of the other planet or otherwise lose the trade route, all your trading will simultaneously come to an end.