You get points for every building in your city, fight you win and good you spend outside of trading.
Every building gives a certain amount of points depending on age, but Great Buildings give more. Ranging from modest points from the Tower of Babel to over 300,000 points on the Space Carrier. Every time you level up a great building you get additional points, of course higher age GBs like a Space Carrier will give more points when it levels up than a lower age GB like Hagia Sophia.
Every won fight gives a certain amount of points too, depending on age. Defeating an army of SAAB units will reward a lot more points than defeating an army of HMA units. That is why higher age players can point farm Guild Battlegrounds more effectively than lower age players.
Also every good spent outside of trading gives points, also depending on age. This includes negotiations in GE, GbG, cMap and quests. Also goods donated to the guild treasury award points (this includes collection from an Observatory, Arc, Atomium, Statue of Honor and Level 11 Airship). Higher Age goods award more points than lower age goods, so donating 10 Stone to the guild treasury wont help you nearly as much as donating 10 Bromine. And negotiating in Bronze Age will not give as many points as negotiating in a higher age.
For specific point values, check the wiki.