Stellaris

• The general agenda of other empires can be deduced by their trait description. Some who f.inst is a "Spiritualist Seekers" will like other spiritual empires, and a "Fanatical Purifier" is probably going to try and kill you at some point. Gifts and deliberately favorable trade deals are usually the only way at first to improve relations, until you can get a treaty which starts building trust.

• When you start making Sectors, look at their planets and see if they lend themselves to a specialization rather than just generic resources. They may have really good energy planets f.inst.

• Lasers beat armor, guns beat shields, missiles beat a little of both and are more accurate, but can be shot down by point defense. Normal guns and lasers are not point defense.

• Energy production is important, even if you have a good surplus throughout the game, a sizable late game fleet can put you in a pretty big deficit if you don't have a large production. The early game you'll probably be feeling more of a mineral squeeze but later on, you'll need energy more. Keep in mind that a fleet costs a lot more upkeep when it is not docked.

• Spaceports and spaceport upgrades boost naval capacity so you should consider building them even in sectors and upgrading them if you need more naval capacity.

• Vassalization can be a good way to boost your military power. Vassals create fleets that will follow your largest stack in wartime. At the least, they'll act as cannon fodder.

• It can very hard with no espionage mechanics to know how to counter enemy fleets, so try for a balance of defenses and the best weapons you have. Space combat is all about having the biggest doomstack, so don't split your fleet.

• Spaceport buildings with ship bonuses only affect ships built there so it can be a good idea to have all the +speed and +evade buildings on the same spaceport that also has corvette assembly yards so you can build tons of speedy dodgy corvettes quickly. Having them spread across multiple spaceports can dilute their effects and make it harder to keep track of which spaceports are good for what.

• When colonizing, generally bigger planets are better, but keep an eye on what direction you want to expand as well, and what resources are around. Settling further out and backfilling is usually not a bad idea, as that gives you control of space. You can extend border range with tech, so "pocket colonies" can reconnect up later.

• Frontier stations are a good choice for securing a strategic resource if there are only small, bad planets (or no planets) nearby. Much cheaper that a colony and doesn't increase your tradition and tech price.

• If you purge an entire planet for whatever reason, leave one pop unpurged, resettle a pop of whoever you want on that planet, then purge the last native pop. Empty planets are just that, empty, and need to be recolonized. Frontier outposts can be used to maintain control of the area, so an AI doesn't beat you to the planet, if resettling isn't an option.

• Research is stored when your scientists are busy with special projects so don't be concerned about falling behind on tech due to projects.

• Techs get much slower if you have a lot of pops so try and keep up with building and upgrading science labs. Likewise the cost of Traditions goes up with the number of colonies you have.

• Look through the Ascension Perks tied to your traditions at the start of the game, and try to pick a few to go for. Some are locked behind tech, so its helpful to decide, which type of endgame you want to pursue, so you can pick the techs as they come up.