Chapter 3, Part 1: PlanetsPlanet -
n -
Latin - Wanderer
Planets are the life and blood of any GL player. Without planets, you wouldn't be able to research new tools, gain new artifacts or pay for your upkeep. Finding planets, taking them, holding them and eventually upgrading hem is one of the most important actions you can perform.
Finding planetsTo find planets, you have to scan them. This can done:

Here
To scan planets, you need a lot of scanning power. The more planets you have scanned, the more you need to find even more planets. You can find ally's planets, enemy planets, and unoccupied planets. No planet is more likely to show up*. However, some types are more and more likely to show up.
When you can no longer scan more planets, the button will turn grey. You need to either get more scan or purge planets from your database with Planet Purgers (another reason why having lots of artifact helps).
*Enemies can put cloak on planets. Your scan must be higher than the planet's cloak for them to be scanned.
Taking planets:Now that you've found some planets (or just kept on reading from the last section). Unoccupied planets can be colonized straight away. Enemy planets must be attacked and have their population lowered to 10 or below. When this happens, the planet becomes invadable. Artifacts such as Engineered Viruses, Ion Storm Charges and the like are very useful when trying to invade planets.
Saboteurs are very valuable when attacking planets. Zolazin Saboteurs can destroy one researchable structure on a planet (population, minefields, shields), if the planets population is below 100.
Holding planets:Planets need defending, or else they can and probably
will be taken. There are a number of ways you can defend a planet:
Shields and minefields: A mix of defense and attack structures. Good at making planets a pain to attack.
Shields and Population: Very effective at slowing down invasions, often making them just to difficult to take the planet (Warning: takes up a lot of space)
Cloaking: Cloak makes planets much more difficult to kill. While not very effective at low ranks, cloak can make planets completely invisible, and thus, untakeable.
In case planets are being attacked, artifacts like Sentry guards and Shield Guards can make an invader's life a LOT more difficult.
Upgradig Planets:This is where some of the special artifacts you can recover from NPCing become useful. However, other artifacts can be used. Chassis's give 1 production point (sometimes 1 in 2 different categories) per 1 space, making them very space efficient. Other artifacts can be recieved from special NPC's, and a list can be found
here, where as chassis's and other run-of-the-mill artifacts can be found
here.
*Part 2: Planet list,
coming soon*