Fuel: different types of fuel are available, the two main ones are hydrogen and anti-matter. Hydrogen is abundant in the universe, and can be gathered by ram scooping stars or gas giants. It provides basic energetic reactions for powering the ships systems, thrusters and hyperspace propulsion. It doesn't cost a lot, but requires re-fueling often, although fuel is cheap. Anti-matter fuel is a lot more expensive, effective and takes less cargo space. Requires dedicated engines in the ship. As it's quite rare, it cannot be directly athered in space.
Gravity generators: most ships are equiped with continuous gravity generators, allowing humans to feel gravity even in deep space. Gravity generators provide a vertical, downwards gravity. For this reason, ships cannot dock on the walls or the ceiling in hangars.