This review provides a general overview of preparation, separation, and analytical methods for cello- and xylooligosaccharides. Arising as side-stream products of different biorefinery processes, these compounds have increasingly gained the interest of researchers and engineers in the last few decades. Beside their application as additives in the food, feed, and pharmaceutical industries, these oligomeric carbohydrates are of key importance as model compounds for studying the dependence of physicochemical properties on the degree of polymerization (DP). First, different preparation methods for mixtures of oligosaccharides with DPs between 1 and 30 are discussed. These methods include acetolysis, acid and enzymatic hydrolysis, and glycoside synthesis. Then, separation techniques, including size exclusion chromatography, normal phase and hydrophilic interaction chromatography, and chromatography on cation exchange resins, are presented. Analysis of oligosaccharides by different techniques is described.