This paper is a first step towards developing a formalism to optimally extract dark energy information from number counts using multiple cluster observation techniques. We use a Fisher matrix analysis to study the improvements in the joint dark energy and cluster mass-observables constraints resulting from combining cluster counts and clustering abundances measured with different techniques. We use our formalism to forecast the constraints in Omega_{DE} and w from combining optical and SZ cluster counting on a 4000 sq. degree patch of sky. We find that this cross-calibration approach yields ~2 times better constraints on Omega_{DE} and w compared to simply adding the Fisher matrices of the individually self-calibrated counts. The cross-calibrated constraints are less sensitive to variations in the mass threshold or maximum redshift range. A by-product of our technique is that the correlation between different mass-observables is well constrained without the need of additional priors on its value.

14 pages, 10 figures, submitted to PRD on 08/08/08. This version incorporates referees' suggestions