Your job is to mop up blood, oil, dust and vomit, replace broken or missing light bulbs and tubes, and pick up litter. It's more fun than it sounds!
Bare minimum requirements: Replace broken lights. If you are going to wet floors, use wet floor signs.
You have the most time consuming, under appreciated and eventually pointless job on the station. You keep small areas from looking shitty while the areas you've already cleaned are covered with blood and litter again. You'll clean floors, toss out junk, replace broken lights and overall, keep the station resembling a workplace and not an anarchist playground!
Drop warning signs where you mop. People get pissed when you don't. You don't have enough to cover every area you clean and between lag and every player running everywhere they're usually not spotted until people are already on their backs, but they can't blame you for doing what you can!
Shaking up those you slipped maintains favour with the crew. Smugly pointing at one of your signs incurs their ire.
The crew tend to be less than welcoming of your efforts to clean.
Also, if people are chasing you, throw a bucket of water behind you, or where they will run into it, as they likely want to steal from you (your shoes are valuable). Or fill your spray bottle with a little water to quickly take down huge amounts of people.
People assume if someone slips, it was your doing. This may not be true. Often it was the chemist with space lube, or a clown with a bucket of water. It's possible to differentiate between slipping on a wet floor and slipping on a lubed floor.
Make sure the detective has cleared a scene before you clean up an area of some blood. Follow people dragging bodies to the medical bay; they leave long trails of blood which means more work for you.
People are going to accidentally charge your cart halfway down the hallway. Kind people will get on the other side of it and push it back to you. There's no avoiding this, apart from not using the cart and relying on the spray bottle, or using the mop with buckets of water held on your person. This would require you to carry signs too.
A janitor cyborg is a far more efficient janitor than you'll ever be. It can clean floors by just moving onto them.
Your mop bucket holds 100 units of liquid. This does not need to be straight water. If you're able to get Chemistry to give you 50 units of ammonia and mix it with 50 units of water, congratulations! You just created 100 units of Space Cleaner and mopping the floor does not leave it slippery. People will still assume that if you're mopping without the signs that you're creating a safety hazard, so make sure to correct them BEFORE they choke you to death.
The bars of soap are a great cleaning implement on the station. They do not run out of ammo like spray bottles do. They can get those hard to reach places (like that vomit under the surgery table) that cleaning grenades can't. You can also use holy water to clean floors; it will not slip people.
Remember that your bottle of Space Cleaner can clean tiles instantly as well. If you aim far enough from your position, you can clean up to three tiles in a single spray. Useful to quickly clean up your evidence.
By right-clicking on the spray bottle, you can tip the contents out of it.
Spray people with space cleaner if they are covered in blood around their head and chest (but not if they have bloody gloves). This usually makes people happy, as security officers won't hound them as much. Sometimes the station needs a hero though; all you need to do is mop the right floor, or spray water at the right time to stop the worst fiend humanity has ever known.
As a traitor you're going to have a hard time. Although you are capable of cleaning up your evidence and prints, you have little access to the station. The best you can do is throw water in front of your target so he falls, drag him into the nearest maintenance tunnel, and beat him dead with a fire extinguisher. Be practical.
Your garbage bag is handy for hiding objects in, as it's rarely checked during a search.
A bear trap can slow someone until someone else is kind enough to remove it from their leg. You don't need a low light area to hide it, you can place it under an object with a large sprite such as a backpack or pizza box, or you can just leave it uncovered and wait for the inevitable runner to zoom into it without time to notice it and stop.
Your light replacer can also be used to set deadly traps. Emagging your light replacer will make all lights you replace be rigged with plasma, causing them to explode when they are turned on. Be cautious though, replacing an active with an emagged-light replacer will instantly cause the light bulb to explode! Turn off the light first!
Your galoshes and spray bottle/mop can be used with water to create visible slippery tiles that cause reasonably long stuns on those who run across them, without slipping you. You can also use your galoshes and your cleaner grenades (which you can order more of through cargo) to create a large area that cannot be crossed by anyone but hulks, traitors with noslips, and you. Anyone caught on the foam area will not be able to move until it disperses without slipping. You can cross the foam and walk into someone to slip them, provided you're moving them onto a foam tile. The foam will stun them long enough to handcuff them, choke them, beat them and cause more knockdowns, or remove their headset.
Your galoshes are no-slips with a small slowdown and it's suspicious of you not to be wearing them. Beg the HoP for chem access (“for more space cleaner”) or break in and fill stuff with lube. Your backpack water tank and spray-bottle can be filled with pepper-spray at the arrivals checkpoint. Just look at those TC savings!
You can often ask the Head of Personnel for more access to clean. This may get you into the department your target works in. You can sometimes dodge a search by claiming you're just there to clean.
You have maintenance access as a janitor, despite the fact you're probably not going to clean there. Most positions don't have maintenance. Use this to your advantage. You also have an escape chute in your custodial closet (your disposal), and a back door that leads into maintenance.