It may be that a particular event or trigger has created a need or desire to seek you out as a potential mentor. The RPS has established a mentoring scheme for its members where you can register and seek out a mentor or indeed offer your skills, expertise and experience as a mentor to potential mentees.
You may also be approached by a trusted colleague in your organisation or, if you work for a smaller employer, someone in another organisation who looks up to you and would value your support and guidance. If you are a prescriber, that may be the route, as may an approach by a newly qualified pharmacist or pre-registration graduate.
You need to be honest with yourself and the person whom you intend to mentor. Have you the time, the skills and experience to devote to making this work? If the answer is yes, then you may find that this is a rewarding experience and the relationship that you create can be life-long.