I would highlight the importance, significance and practical application of the research he is going to undertake. Also, identifying and presenting the transferrable skills that grad students will develop during their research might motivate the students.
Sir, I myself being a graduate mechanical engineering student find many difficulties in the field of research. Being a fresher, I often ask for advice from my seniors and faculties, while some of them help while some don't. According to me, the primary problem is the interest of the individual and his surroundings.
Students truly love the things they are capable of creating for themselves. Teachers who are able to involve their students in research processes, offering them participation within the scope of their knowledge, within a research process, is the best way to motivate them to investigate and is the best way to train a researcher. We all want and need recognition. If the teacher as a scientific and academic leader, appears in research with his students, these students will have the incentive to create scientific contributions.
I think the advisor can greatly inspire a fresh researcher by discussing the research ideas and motivate him/her by giving some simple tasks in the beginning. Once the student gets on the track, let him swim in the ocean of knowledge.