I always ~
Wash FQs and yardage. Pink the edges, then machine wash by colour (ex. all blues) in hot water with colour catchers. After checking colour catchers, machine dry on low or rewash.
Clean the bobbin area and put in a new needle at the start of a new project.
Make a sample to be sure pattern directions are correct. Especially if it's a kit and the yardage is no longer available.
My Mom always said "Do your very best or don't bother!" It's important to me that points match and are not cut off. I'm definitely not in the galloping horses camp. https://cdn.quiltingboard.com/images/smilies/smile.png
Unplug the iron if I leave the room.
All electronics are plugged into a surge protector: I unplug everything including the surge protectors during thunderstorms.
I usually start quiltmaking at 10 AM and always stop by 4 PM or earlier if I get tired.

My one unbreakable rule is when someone is showing a finished quilt - whether just to me personally or in a group such as a guild meeting. And I see an error, mistake, or anything that I think doesn't look right. I point it out to the owner of the quilt unless she/he specifically asks me to point out mistakes and then only in private.
I have been at guild meetings when someone is showing her finished quilt and there are a couple of people in the guild who seem to take great pleasure in publicly pointing out things like - that block is upside down, did you mean to switch the colors in the middle of the 3rd block from the left in the middle row? To see the look on the face of the presenter can be heartbreaking, especially if they are new quilters.

I have a few rules in my sewing room....

Always close the rotary cutter when you put it down.

Never place a drink on the sewing machine table.

Always oil my midarm between every bobbin change and then use a quilt sandwich to soak up oil before working on my quilt.

Always make an extra block or two to make into an exact replica of the quilt with batting and backing to use to check tension.

Put fabric on the straight of grain before cutting.

Watson

Not really rules, but some habits.
1. I oil the hook on my SweetSixteen every time it needs a new bobbin- got into that habit after hearing the terrible sounds it makes if I don’t (yikes!).
2. unplug my iron at end of day even though it is plugged into same surge protector as the lights. So if lights are off, iron is off, but I got into the habit of unplugging iron years ago before surge protectors were a thing.

Rob

My only rule is after I make the same error three times, stop for the day.

i bet you wrote "not" in caps here: I point it out to the owner. Kind of changes the meaning.

I've had the same thing happen. If one wants to emphasize a word, caps are not permitted on QB and the word will be removed from the post, even though caps are a common usage. On most sites it's the entire post or sentence in caps that's more commonly considered shouting. I think italics or bold are permitted here. Maybe *asterisks* as well.

I have a few rules:
- If you need to ask if something should be "fixed" then just fix it - otherwise it will always bother you. It's always to fix now than when the quilt is further along.
- Be kind, supportive and respect all quilters including yourself.
- Never rush or sew when you are tired ...we all know what happens...
- No food or drink except water in my sewing area. I'm a klutz.
- Press and measure each unit - it makes a huge difference.
- Enjoy the process. (This is hard for me as I easily get frustrated and want to abandon the project when there are problems. I am gradually learning to enjoy the process through the good and the problems.)
- Listen to the Quilt Police but only if they are offering ways to help me improve my skills. (Some of their advice is great.)

No pink, no flowers, nothing cute, childish, or feminine. Most of my lap quilts go to the VA hospitals. An occasional bit of of pink or flowered fabric in a scrap quilt is OK, but I'm not to make some poor guy sit there with big pink flowers or bunny rabbits covering his legs.

No one ever goes into my sewing room - other than to look at my quilts,etc.

The one and only rule I have for myself is keep my secrets to myself.