I'm a long time KSP player and forum lurker, and love this thread. Here are mine:
I saw this mentioned briefly once earlier and had to post in agreement: KSP is best played for me with a pencil and notepad handy (and frequently used). Especially in Career mode when trying to get the most cost efficient performance out of my designs, I record my ascent profiles and de-orbit profiles to refer to in the future for adjustments - or to nail that perfect return from orbit to the KSC runway. I jot down design changes to make for future flights based on performance. Heck I even map out goals and order of contracts in a launch schedule format. Like any sandbox game I find the goals i set for myself are what makes it engaging and keeps me coming back for more.
Playing Career with quicksaves turned off is a real adrenalin rush! I sometimes hate myself for playing this way but it's also given me some of the best gaming moments ever in a lifetime of gaming.
Finally, two mods I never fly without: KerbalEngineer and Chatterer.
