#POSCAR
From JARVIS database (OptB88vdW)

#KPOINTS
Converged from JARVIS database

#POTCAR
PAW_PBE GW pseudopotentials

#INCAR DFT
ISMEAR =  0
SIGMA  =  0.05
EDIFF  = 1E-8

#INCAR DIAG
# Frequency dependent dielectric tensor without
# local field effects
ALGO = Exact
NBANDS  = 64
LOPTICS = .TRUE. ; CSHIFT = 0.1
NEDOS = 2000
# you might try
#LPEAD = .TRUE.

ISMEAR =  0
SIGMA  =  0.05
EDIFF  = 1E-8

#INCAR GW
# Frequency dependent dielectric tensor including
# local field effects within the RPA (default) or
# including changes in the DFT xc-potential (LRPA=.FALSE.).
# N.B.: beware one first has to have done a
# calculation with ALGO=Exact, LOPTICS=.TRUE.
# and a reasonable number of virtual states (see above)
ALGO = GW0 ; LSPECTRAL = .TRUE. ; NOMEGA = 50

# be sure to take the same number of bands as for
# the LOPTICS=.TRUE. calculation, otherwise the
# WAVEDER file is not read correctly
NBANDS = 64

# Add this to update the quasiparticle energies
# in the Green's function (GW0)
NELM = 4

ISMEAR =  0
SIGMA  =  0.05
EDIFF  = 1E-8

Sample workflow script attached
adapted from https://www.vasp.at/wiki/index.php/Bandgap_of_Si_in_GW
