Tolerance stack-ups should be considered on mating parts. Overall assembly tolerances should be calculated, and interface as well as clearance requirements understood. Surface finish requirements can be established based on actual manufacturing processes employed however, surface finish requirements should be understood and design intent accurately defined. Simplify design and assembly so that the assembly process is unambiguous. Roll pins, dowel pins or offset mounting holes can be employed.
Examples are dowel pins.
Product design must avoid parts that can become tangled, wedged or disoriented. Verify clearance for assembly tooling such as hand tools and fixtures. With hidden features that require a particular orientation, provide an external feature, guide surface or design alignment fixturing or tooling to correctly orient the part. Design in fasteners large enough that are easy to handle and install Design for efficient joining and fastening. Consider design alternatives that will reduce fastener count.