How to start
Define linear parameters for vacuum tube.
Use Averaged Anode-Grid characteristics of the tube (picture 1).
Remember, that using of the left quadrant of tube characteristic provide linear amplification with minimum intermodulation distortion.
The using of the  left quadrant provide a minimum grid 1 current.

Draw a line from point "a" along  curve of current to meet point "b" (red line a - b in the picture 2). 
Point "a" is the highest peak current in the left quadrant.
Reflection perpendicular line from point "b" give you point "c" . Line drawn  from point "c" perpendicular to scale "Ia pk"  shows
zero-signal current  providing linear amplification.
It is applicable for grid driven amplifiers.

If your project is cathode driven amplifier, you may divide defined  zero-signal current for grid driven amplifier to 6 - 8 times.
For example, zero-signal current for grid driven amplifier is defined as 0.3A,
that means that zero-signal current for cathode driven amplifier is 0.3A / 8 = 0.0375A
You may choose any zero-signal current, but not less than 0.0375A.
For example, it might be around 40 - 50mA

Driving voltage 32V pk in this diagram provide maximum anode current Ia pk = 1.7A.
It is too high current for the tube. Real maximum current could be defined by software to avoid damage of the tube.
This diagram will be useful for next calculations to define driving voltage and other grid parameters.

Important: the curves of the current in Anode-Grid characteristics  can be moved more to the  left if screen voltage is increased.
Use it to avoid grid 1 current and to get highest anode current and linearity.