Without reading all the other posts...
Buy nice tools. Spend more up front for the nice stuff. Buy a top-notch tool sharpener.
I like mandrel savers from PSI. Places the compressive load from the tailstock on the bushings instead of the mandrel - if someone should over tighten the tailstock hand wheel.
I press all my pens on the lathe with
these pen press adapters. Cheaper than a pen press and insanely more accurate due to the fact that you can precisely control the press with the hand wheel on the tailstock.
Focus on accuracy, fit, and finish. Illuminate the work area near the lathe to more easily identify flaws in the finish. I have a 2' 2400 lumen T-5 above just above my lathe.
You can build a house and be off quite a bit everywhere, still get the house built, and hardly anyone will notice. When making a pen your tolerances are in the thousandths. A few thousandths off at the nib and the user will feel it EVERY time they hold the pen. Digital calipers. Buy some. Use them.
If you've taken the time to turn a nice blank don't take a shortcut on the finish.
Basically, it's like I tell my kids. If it's worth doing, it's worth doing to the max of you abilities. No sense in going into a project with intent to half-ass part of it.
Don't take shortcuts.
If you don't know something research and ask questions.
Buffing (Beall 3-wheel system on the lathe) is worth it. I use tripoli and white diamond then use the carnauba wheel as a final clean/buff without wax. Every pen I make - whether I sell it for $25 or $150+ gets buffed. Acrylic, wood, bone, everything. Buffing makes a difference.
Which brings me to...use the SEARCH. Between the IAP library and the search function I can't count the hours I've spent reading between April (when I started penturning) and now.
And remember that no matter how good you think you are, you can always be better. Never settle for good enough. Keep pushing yourself to progress. If you find yourself doing the same pens without experimenting with new stuff, you've stalled and you're letting yourself down.
It's worth failing a time or ten to make a pen that's awesome.
Work with great woods. I like to work with burls because the grain sells the pen. I apply the same theory to pens as I did to being an assistant editor for magazines - people are drawn in by visual cues. No text I could put on the cover would make people pick up the magazine - it's awesome photography that will grab their attention. Same deal on the inside. Awesome photography will keep their attention when they flip through at the newsstand - strongly written editorial has to support the photography.
With pens there are two things that will draw attention - either the blanks or the hardware.
This Victorian in Amboyna has both an awesome blank and nice hardware. While some have said it's a bit too much, I think it has enough for people want to pick up and admire the pen just for the fact that there is a lot to look at.
After you've made some pens carry them and use them. Everywhere. It's not often people stop and say "Wow, that's a nice pen." When you can make that happen you're doing something right. Several guys here have sold the pens out of their pocket.