Easy. Firstly they have to have a 2(1) or 1st class degree to get a grant (currently £13,500 pa tax free – not bad!) and then I look for enthusiasm. I can teach the ins and outs of the project but I cannot make someone enthusiastic and you need that to go the extra mile in a PhD project. Read some of Jack’s responses to questions if you want to see what an enthusiastic PhD student is like.