Domain & resolution

First you should decide if your final(!) simulation (see "Cascading" below) should be on a regional or a global grid and at which resolution you want to run. For this it is important to know that:

the more grid points a grid has, the more cores are needed and
the smaller the resolution and with that the model timestep the longer the simulation will take.

Number of points

Topology (MPI & OpenMP)

Resolution → timestep

The relation between the horizontal resolution and the model timestep is linear. Here are some examples:

Resolution [degree]	Resolution [km]	model timestep [sec]	For GY grid
0.009°	~1 km	30 s
0.0225°	~2.5 km	60 s
0.036°	~4 km	90 s
0.11°	~12 km	300 s
	~25 km	720 s	Grd_nj = 417
	~55 km	1800 s	Grd_nj = 171

Resolution → timestep → radiation timestep

Resolution → (non) hydrostatic

Model levels

LAM grid → top piloting or sponge

Global grid → adjust global pressure

Cascadeing

Spectral nudging

Period

Greenhouse gases

Initial conditions

Driving data

Geophysical fields

Schemes

Land surface scheme (ISBA, CLASS, SVS)

Lake scheme (non, FLake, CSLM)

Urbain scheme (non, TEB)

Roughness length

Limit ice /snow

Gravity wave drag

Emissivity

Condensation

Convection

Tracers to advect

Precipitation (Bourgouin)

Boundary layer

Horizontal diffusion

Output fields

Instantaneous / averages / min / max

Initial condition fields

Pilot fields (2-D / 3-D)

Output frequency

Output levels

Size of output files (monthly/daily/hourly/...)