The current state of the Web, which is dominated by centralized cloud services, raises several concerns on different aspects such as governance, privacy, surveillance, and security. A way to address these issues is to decentralize the platforms by adopting new distributed technologies, such as IPFS and Blockchain, which follow a full peer-to-peer model. This work proposes a set of guidelines to design decentralized systems, taking into consideration the different trade-offs these technologies face with regard to their consistency requirements. These guidelines are then illustrated with the design of a decentralized questions and answers system. This system serves to illustrate a framework to create decentralized services and applications, that uses IPFS and Blockchain technologies and incorporates the discussion and guidelines of the paper, providing solutions for data access, data provenance and data discovery. Thus, this work proposes a framework for the design of decentralized systems and contributes a set of guidelines to decide in which cases Blockchain technology may be required, or when other technologies, such as IPFS, are sufficient.