Random search within a bounding box is a good baseline method (Bergstra 2012). Bayesian optimization methods can also be applied, see here for software implementations. See also Wikipedia - Hyperparameter Optimization. When publishing, it is recommended to report the method of tuning hyperparameters, the bounding box, and number of hyperparameter evaluations (Dodge 2019).
See also list of software in Ch 10, p. 322 (p. 51 in pdf) of HOML.