Lithographically fabricated circuit patterns can provide magnetic guides and microtraps for cold neutral atoms. By combining several such structures on the same ceramic substrate, we have realized the first ‘atom chips’ that permit complex manipulations of ultracold trapped atoms or de Broglie wave packets. We show how to design magnetic potentials from simple conductor patterns and we describe an efficient trap-loading procedure in detail. Applying the design guide, we describe some new microtrap potentials, including a trap which reaches the Lamb–Dicke regime for rubidium atoms in all three dimensions, and a rotatable Ioffe–Pritchard trap, which we also demonstrate experimentally. Finally, we demonstrate a device allowing independent linear positioning of two atomic clouds which are very tightly confined laterally. This device is well suited for the study of one-dimensional collisions.