  We present the steps to forecast the sensitivity of the Laser Interferometer
Space Antenna (LISA) to both a stochastic gravitational wave background and
deterministic wave sources. We show how to use these expressions to estimate
the precision with which LISA can determine parameters associated with these
sources. Tools are included to enable easy calculation of the signal-to-noise
ratio and draw sensitivity curves. Benchmark values are given for easy
comparison and checking of methods in the case of two worked examples. The
first benchmark is the threshold stochastic gravitational wave background
$\Omega_{GW} h^2$ that LISA can observe. The second is the signal-to-noise
ratio that LISA would observe for a binary black hole system identical to
GW150914, radiating 4 years before merger.
