This review is conceived as an introductory text to aid in the understanding and conception of fluorescence-based measurements of biomolecular interactions. The major fluorescence observables are introduced briefly. Next, the criteria that are involved in the choice of the fluorescent probe are discussed in terms of their advantages and disadvantages for different types of experiments. The last sections deal with the experimental design for fluorescence-based assays aimed at detecting different types of biomolecular interactions. Included in our examples are protein-ligand interactions, protein-nucleic acid interactions, aqueous phase protein-protein interactions and protein interactions in or at the cell membrane. We hope that this introduction will be of use to students and researchers considering the use of fluorescence in their work.