There are several different environments on every map of stellar impact that effect ships in some way.
Tactics: The battering ram skill can be used to take advantage of asteroid fields as enemies won't follow you in. Asteroid fields only inflict damage while moving, so sitting still in one can be a useful tactic, especially for artillery ships. Keep in mind that you are a sitting duck if you are caught in the middle of the field.
Asteroids cause critical damage to every ship flying into them. They can be destroyed for cp.
Tactics: Use for cover in firefights if you are at a disadvantage. Use quantum leap to jump lines of asteroids to take advantage of shortcuts on the map. Killing asteroids give CP, so while not every efficient, it is possible to farm them. However if you wish to farm asteroids, it is suggested you use the Gunner's passive skill mining charges, which increases damage to asteriods by 100%.
Plasma fields slow ships by 30%. Slowing penalties can be reduced via the passive skill evasive maneuvers.
Tactics: Try to lead larger enemy ships to plasma fields if possible. Enemy squadrons can be evaded by entering a plasma field and using quantum leap/quantum accelerator to get out.
Gas clouds cloak ships. You are decloaked when firing weapons as long as you dont use proton turrets. Every skill that decloaks ships like radar beacon or scanner also reveals you when you are in gasclouds. Other ships in gasclouds can also see you.
Tactics: If an enemy ship is entering a cloud you are in, take the drop on the enemy with torps or shockwave. Good place for quantum beacons and support structures.
Being in the gravitational field of a star damages shields and squadrons. They also pull you torwards them.
Tactics: Many maps are set up that rushing through the star is a plausible last-ditch effort. In normal combat, use stars to get squadrons off and getting slow ships to lose shields.