  TESS is expected to discover dozens of temperate terrestrial planets orbiting
M dwarfs whose atmospheres could be followed up with the James Webb Space
Telescope (JWST). Currently, the TRAPPIST-1 system serves as a benchmark to
determine the feasibility and resources required to yield atmospheric
constraints. We assess these questions and leverage an information content
analysis to determine observing strategies for yielding high precision
spectroscopy in transmission and emission. Our goal is to guide observing
strategies of temperate terrestrial planets in preparation for the early JWST
cycles. First, we explore JWST's current capabilities and expected spectral
precision for targets near the saturation limits of specific modes. In doing
so, we highlight the enhanced capabilities of high efficiency readout patterns
that are being considered for implementation in Cycle 2. We propose a partial
saturation strategy to increase the achievable precision of JWST's NIRSpec
Prism. We show that JWST has the potential to detect the dominant absorbing gas
in the atmospheres of temperate terrestrial planets by the 10th transit using
transmission spectroscopy techniques in the near-IR. We also show that stacking
$\gtrapprox$10 transmission spectroscopy observations is unlikely to yield
significant improvements in determining atmospheric composition. For emission
spectroscopy, we show that the MIRI LRS is unlikely to provide robust
constraints on the atmospheric composition of temperate terrestrial planets.
Higher precision emission spectroscopy at wavelengths longward of those
accessible to MIRI LRS, as proposed in the Origins Space Telescope concept,
could help improve the constraints on molecular abundances of temperate
terrestrial planets orbiting M-dwarfs.
