Don't be afraid to ask questions then take what you need from the answers given and move on. As a young quilter I was pretty inexperienced and appreciated much of the advice I got when I asked questions. For a very long time I got hung up on "rules" people told me at the local quilt shop when I asked questions. Imagine my surprise and delight when I realized I could do whatever I wanted and the quilt police weren't going to come and take me away! :)

I piece with all colors of thread even bright red. Of course if I'm using all white fabric I use white thread. Purple, green, yellow, blue or orange thread blends in just as good as any neutral when piecing scrappy quilts or mixed fabric quilts. I like pretty colors of thread.

I really don't see the need to spend time to cut up scraps into squares. Not all of the shapes I use are square in any case and I would rather leave as much of the fabric as possible so that I don't waste anything. Any material that is not used for quilting can be made into interesting yarn.

I keep scraps for applique' which often only needs the small bits. They're jumbled in a shoebox. Who cares? If I need it, I'll iron it.
Larger scraps don't get cut into squares. Tried that. They're still squares. And probably will be for a Looonnnnnggg time! My larger scraps stay together...all colors...I sort through when I'm making a prayer pocket quilt.
I do try to make my quilts the best I can.
Instead of following 'don'ts,' try the 'dos.' As in do:
enjoy quilting, keep learning new ways, get rid of things you're not going to finish, take pride in your work, enjoy meeting other quilters.

My major "don't" for new quilters is Don't be intimidated by others telling you this project or that project is too hard for a beginner.

Another don't for me is don't let other quilters scare you away from things like curves, bias edges, too small or too large, hand vs machine, etc.

And don't feel like you have to buy every gadget you see that looks cool!

I go to a UFO camp evert July. That's how I get rid of my UFO's.

I don't follow rules in my quilting, I do that in the rest of my life areas (pay my bills, taxes, obey laws, etc.) My quilting and sewing is for fun and relaxation, I do things the way I want to!! I put my scraps in a big round tub I got at Walmart, it just slides under my quilting frame out of the way, I pull it out when I want to use it.

Be sure your cutter is sharp enough for the amount of fabric you are cutting. Much less chance of a slip and nasty accident.

NEVER say never

and

ALWAYS keep an open mind to different ideas and techniques

Don't be afraid to try something new. I have been quilting for about 4 years and there are many techniques I have not yet tried. Something to look forward to, but if I like a pattern, I make it again, knowing what mistakes I made and how I can make it bigger/smaller. Learning is the key - keep on and you will stay young.