The programme to design plasma scenarios for the Spherical Tokamak for Energy Production (STEP), a reactor concept aiming at net electricity production, seeks to exploit the inherent advantages of the spherical tokamak (ST) while making conservative assumptions about plasma performance. This approach is motivated by the large gap between present-day STs and future burning plasmas based on this concept. It is concluded that plasma exhaust in such a device is most likely to be manageable in a double null configuration, and that high core performance is favoured by positive triangularity plasmas with elevated central safety factor, while external heating and current drive is provided most effectively by microwaves. The gap between existing devices and STEP is most pronounced in the area of core transport, due to high normalised plasma pressure in the latter which changes qualitatively the nature of the turbulence controlling transport. Plugging this gap will require dedicated experiments, particularly on high performance STs, and the development of reduced models that faithfully represent turbulent transport at high normalised pressure. Plasma scenarios in STEP will also need to be such that edge localised modes either do not occur or are small enough to be compatible with solid material lifetime limits.