Proposed MIMO and hybrid MIMO/phased array (HMPAR) radar systems have the potential for tremendous flexibility in the choice of the transmit beampattern, through the selection of multiple transmitted signals. This paper considers how one might exploit that flexibility in light of prior information or uncertainty in target spatial location, for parameter estimation or tracking applications. We first consider an idealized problem of distributing energy across multiple target sites given a prior probability distribution on those sites. It shown that the optimal allocation of energy would be proportional to the square root of the prior probability. Second, we propose a method to approximate this optimal distribution of energy using a MIMO radar or HMPAR radar system. The method chooses signals that realize an intrapulse beamscan over the region of interest, with a nonuniform distribution of scan points matched to the desired distribution of energy.