NOTE: WFPC2 has been removed from HST, and is therefore not available for proposing new observations. Archival Research proposals using existing WFPC2 data are of course supported.
The HST General Observer proposal process is divided into two Phases. Phase I proposals contain a scientific justification and abbreviated technical specifications for review by the Telescope Allocation Committee in a particular Cycle. Phase II proposals provide many more technical details for programs recommended by the TAC and approved by the STScI Director for implementation. The information required by proposers for Phases I and II are provided in the links, below.
The Astronomers Proposal Tool (APT) will be of great utility for both Phases.