Lab Citizenship is a catch-all term that describes some of the unwritten rules of working in a lab. As such, this section is mainly of interest to those who've never worked in a lab or have only worked on the dissecting teams, and may be old news to anyone else. In any case, they're largely common sense practices based on the ideas of what goes around comes around, and of keeping things running smoothly in a busy, crowded work environment. That being said, if you are new and have not read Lab citizenship rules to live by, read it when you finish this. The time you spend reading will be much shorter and more pleasant than the interaction you're likely to have the first time you unwittingly break one of these rules.
With other people's tools or reagents: don't use or borrow something from anyone else without talking to them first, even if you'll just be putting it back or replacing it "right away". The equipment you borrowed may have been for RNA use only, or the tube you used may have been their last, for a special experiment the next day. Also, if you've talked to them, in the unlikely event that you forget to return it, they'll know who to look for. If you're in a jam, remember there is a cell phone number list posted in the lab so you should still be able to reach the person whose tool or reagent it is.
My rule of thumb is to leave myself an un-missable note, email reminder, etc. to return something if I've moved anything around, and not to count on myself to remember to return it without a reminder note (or two). It's better to err on the side of overzealous caution than to find yourself guilty of moving a piece of equipment, whether it's a desk chair or a pipettor or anything, and leaving someone else unable to find it- you definitely don't want to become known as the person to turn to whenever something can't be found where it should be.
If you need the last of a shared enzyme, sleeve of plates, etc., but aren't sure how new ones are ordered or replacements made, it's best to stop and sort that out first before proceeding. If you put it off, only to then finish your experiment and forget about it, it may not get noticed until the next person comes up short.
For equipment: If you need to change the settings on a shaker or incubator, or use a piece of equipment you haven't used before, it's best to find a current user of that equipment to talk with first. Some older lab equipment needs a special touch, or no longer works on all of its original settings, and some things may need to stay set at a certain speed or temperature for reasons that are far from immediately obvious.
These specific examples give you the basic gist of the type of thinking that keeps people working together smoothly. Whenever in doubt, always ask, and you'll be all set. And agin, if you have not yet read the Lab citizenship rules to live by, read them before you do ANYTHING else. Again, the time you spend reading will be much shorter and more pleasant than the interaction you're likely to have the first time you unwittingly break one of these rules.