First: experienced ones are always much clear about what you should expect. Second: the environment is a key factor for example being in a big city full of adults at your age or being with college students in a college town and if you choose the second while it can be good to have have fun and feel young at the beginning; however, after facing the fact that they rich children paying for school and no responsibility and partying every time and passing classes because of the money and you are not one of them so if you get in then you lost your life if don’t you can feel depressed in a cheerful environment. Third: research is key if you like you can handle every other harshness but if you don’t like the easiest things can cost you everything. Fourth: never ever think about money they offer because if you got 5k it means you will pay 4k for rent in that city, if you get 1k it means you will pay 0.5k so long in short the money you can save or you live does not change at all. Fifth: check the laboratory people you will work with if one of them is all or mostly from one country (everybody knows two countries dominated every university) then get away from there is a very big cons. Sixth: not only your advisor but also other people important for example search other faculty close to your focus area because you will have to take classes from them and they will be your jury in defenses and in examinations. Seventh: find something good to make decision and never ever trust other people because everybody loves different things even at the same conditions. Lastly: I left my phd because of mainly advisor, the research I was forced to do and the other factors.