We address the problem of automatic synthesis of decision procedures. Our synthesis mechanism consists of several stages and submechanisms and is well-suited to the proof-planning paradigm. The system (adeptus), that we present in this paper, synthesised a decision procedure for ground arithmetic completely automatically and it used some specific method generators in generating a decision procedure for linear arithmetic, in only a few seconds of cpu time. We believe that this approach can lead to automated assistance in constructing decision procedures and to more reliable implementations of decision procedures.