This text discusses the high-resolution NMR of liquid samples and concentrates exclusively on spin-half nuclei (mainly 1 H and 13 C ). It is aimed at people who are familiar with the use of routine NMR for structure determination and who wish to deepen their understanding of just exactly how NMR experiments work. It demonstrates that in NMR it is possible, quite literally on the back of an envelope, to make exact predictions of the outcome of quite sophisticated experiments. The experiments chosen are likely to be encountered in the routine NMR of small to medium-sized molecules, but are also applicable to the study of large biomolecules, such as proteins and nucleic acids.