When u choose your project, be careful that you are really motivated by the topic and will still be in 3 years time. And most importantly, the supervision. Is there anyone to supervise you properly? Can u ask anyone for help when u have technical problems, I think that's the most important, not to feel left alone during PhD.
And last but not least, make sure that there is someone to train you on the devices you will use or on the techniques that you are "supposed" to know. Or someone you may ask when you have problems. Because I think PhD is personal matter but it is still part of your education and formation. Learn the most u can from it.