My first piece advice to prospective grad students would be to find a lab or an advisor that you mesh well with and are excited about working with. If you are on the same page and feel comfortable from the start, it makes all the difference. After that, trust yourself and your abilities! You are capable of more than you think.
My best advice for prospective grad students would be to not be afraid to put yourself out there to the individuals you want to work with or those you believe to be the best sources of information. You are your best advocate! I would suggest doing as much research as possible on different graduate programs at various institutions, as well as the research being conducted to find the best fit for yourself. In my experience, asking current grad students how their experience was and how they achieved their goals was extremely helpful as they provided their authentic opinion.
This is a program that is very responsive to student needs, so if you have a question or want to pursue a line of discussion, be sure to ask! There is a considerable commitment to participants' career and personal growth, as well as to the more formal education elements. I appreciated that "all-around" approach.
To future graduate students, it is important to keep a clean, legible, and logical lab notebook! Also remember that your brain is your best weapon to succeed in graduate school and it functions best when it is well-rested; only pull all-nighters if necessary. Learn to manage your time and try not to do multiple things at once; multi-tasking in the lab can lead to errors in experiments. Finally, enjoy your time and get all the food and freebies from conferences and other events!