Turbulent thermal convection which occurs due to the temperature differences imposed at the boundaries of the domain is omnipresent in nature in technology. In this talk, we will consider three classical setups, namely, Rayleigh-Benard convection, vertical convection, and horizontal convection. For these systems, we will discuss the scaling relations of the global heat and momentum transport, the proper boundary layer equations, and the large-scale flow organization. We will show that in some cases, the scaling of the global heat transport and the temperature profiles can be predicted by solving the proper boundary-layer equations that include turbulent fluctuations and correct boundary conditions. Further, we will discuss the global flow structures in turbulent Rayleigh-Benard convection in slender and wide containers. We will see that the self-organized turbulent flow takes the form of several convection rolls on top of each other if the container is slender or in a form of convection rolls that are attached to each other in a horizontal direction if the container is wide. The shape of these rolls strongly influences the global heat transport in the system. Finally, we will explain the reasons why the size of the self-organized rolls is quite restricted.