There are two types of phone interviews I've experienced.
1. Literally just a standard interview. Just prepare as you would a standard interview, and keep some notes out in front of you. However, grad recruitment are aware of this so they try and ask questions which you wouldn't have prepared for. Also make sure you don't recite what you have in front of you.
2. Situational strengths. Basically a situational judgment test. There's no real way you can prepare for this; though practicing some situational judgment tests may give you an idea on how to reply.
Often they combine both the above.
In my experience, I tend to find phone interviews significantly easier than video interviews (though not sure what the general consensus is).
At the end of the day there's nothing quite like experience. So if it doesn't go well, don't worry about it, just apply what you learnt for the next one. What I would say that is as soon as you finish the interview you make a note of all the questions asked, especially the one you struggled with.