With recent advances in mobile technologies and infrastructures, there are increasing demands for ubiquitous access to networked services. These services, generally known as m-services, extend supports from Web browsers on personal computers to handheld devices, such as mobile phones and PDAs. However, in general, the capabilities and bandwidth of these devices are significantly inferior to desktop computers over wired connections, which have been assumed by most Internet services. Instead of redesigning or adapting m-services in an ad-hoc manner for multiple platforms available in handheld devices, we propose a methodology for such adaptation based on three tiers: user interface views, data views, and process views. These views provide customization and help balance security and trust. User interface views provide alternative presentations of inputs and outputs. Data views summarize data over limited bandwidth and map heterogeneous data sources. In addition, we introduce a novel approach of applying process views to m-service adaptation, where mobile users may execute a more concise version or modified procedures of the original process. The process view also serves as the key mechanism for integrating user interface views and data views. In addition, we present a formal model on view consistency and integrity in our methodology. We demonstrate the feasibility of our methodology by extending a service negotiation subsystem into an m-service with multi-platform support.