1) Select your supervisor with utmost care. Never go for too young and too old people.
2) Always check publications: Not only where do they publish but who publishes. Do all of them get a chance to publish? For e.g.: do masters/PhD student get a chance to publish? Its always good to get published as an equal contributing author or as first author.
3) Check your compatibility with other lab members. If you feel they will push you down then think twice before joining.
4) check the grant status of the supervisor if he can fund you for your complete PhD.
5) Check the lab if the equipement they are using are outdated and if outdated can they buy new ones as some grants like EU grants don’t allow to buy new equipments using the grant money.
6) Also remember, the supervisor may push you down or derogate you while writing recommendation letters if you have done better work and have good publication. BE CAREFUL OF THEM.
7) Try to utilise your skills and try bringing something new techniques to the lab you are joining.

Try to collaborate with other labs
9) Don’t be a workaholic. Have time for yourself, follow your hobbies, socialize and if you have a family spend time with them.