I've done it! I've gotten my Ph.D.! Here's a few things I wish I had done from the very beginning.
You're going to take 4-8 years investing in yourself. This is time you've set aside to educate yourself about a subject you're hopefully passionate about. Along the way, you'll learn a tonne about a multitude of subjects! Besides a lot about turbulent mixing, I learned how to ski, how to operate a metal lathe, how to clean an ion-laser, a lot about relationships, how to build and program a robot from scratch, etc. (The list could go on forever). Embrace and enjoy it. Motivation and feelings towards your research will ebb and flow, but this is a big part of your life!
No detail is too small, and you will forget even what seems the clearest! I can't tell you how many times I re-wrote the same bit of code, or re-did an analysis or thought myself in circles because I didn't write something down. I wish I had spent 30 minutes at the end of every day writing down what I did that day, and attaching a few photos if I took an experiment setup. Making a google form and using tools like evernote are really useful for this. Just find a system that works for you!
Start Writing your Dissertation NOW!
This ties into the previous tip, and although it seems every Ph.D. puts off writing their Dissertation until six months till their thesis due, I can't tell you how much easier and better my thesis would have been if I had taken some time every couple months to work on my thesis. This could include plugging papers you're reading into your literature review sentence (Some will only get a sentence in your thesis), summarizing an analysis you've done in an appendix, or writing up a methods section after you get a successful data set.
Find a Reference Manager
When you read a paper, record highlights and jot down some notes. Some papers I just skim, while others I read more than ten times. But for every paper your eyes glance at, save a PDF and jot down some notes. There are plenty of tools to help you stay organized: I use Mendeley however I also have good things about Sente, and Papers.
Write your thesis in LaTeX.
I'm soo glad I used this. There is a learning curve over processors like Microsoft Word, but it made formatting my thesis and bibliography a no-brainer.
Find a support network.
A Ph.D is no small feat, and will result in some emotionally trying times. Many universities have dissertation support groups which i've heard great things about. I found private counseling with a psychiatrist to be invaluable in maintaining sanity and emotional stability, especially in the last year of my Ph.D. My wife, church, friends, and family were also great resources.