Things I wish I knew/did earlier in grad school

Keep a journal of every research-related idea you have and every research-related action you take. Seriously, find the most frictionless way you can keep notes and stick to it. Your brain will thank you later.
Ask for help whenever possible, but with the knowledge that many of the issues you have will have no troubleshooting manual.
Crude, hacked together and done is better than perfect and never finished.
Work when you feel productive. Sleep when you feel less productive. Use the benefits of being a self-scheduled researcher to your advantage.
Don’t feel guilty to be involved in grad student life and service. These activities give a mission and direction to your research.
Take on a mentee. It is such a massive boost to your own productivity to take charge of managing and encouraging another less experienced person’s work. It will push you to practice what you preach.
Make sure your family and loved ones know what you do and what is expected of you, so they aren’t upset when you aren’t free to talk or have to work a late night.
Don’t hold on to the paper you’re working on too long. Chances are that there is someone out there doing a similar project based on an idea that they had at the same time as you, and you don’t want to get scooped.
If someone more experienced than you who you respect disagrees with your findings, that doesn’t mean you’re wrong.
Don’t be afraid to overhaul a project you have based on new information. This is the stage of your career when you are not invested in a theory or particular method. You can quickly change tack to use new analyses and pursue new research questions with little or no cost. Your committee will understand.
NEVER show off how much you work. We all work a ton (yes, you do too, don’t let that impostor syndrome get you) and there is no need to hero-worship based on how many hours we work a week.