This chapter develops a general approach to steady-state flowsheeting, in a manner independent of a commercial simulation package. The user should be able to use efficiently any simulator after becoming familiar with some specific technical elements. The approach to solving a flowsheeting problem is explained by means of an example, the toluene hydrodealkylation process. The next section describes the generic capabilities of the flowsheeting software. Then, a large section deals with degrees of freedom analysis, an important topic in ensuring adequate specifications both for the simulation units and for the whole flowsheet. A section on methodology describes how to solve convergence problems, and how to use control structures to bring the simulation closer to the industrial reality. A final section deals with analysis tools, such as sensitivity, case studies and optimisation.