> - don't redesign anything, do a port (see also, Typescript compiler to Go port)
> Don't get tempted into doing refactorings as you go.
I would say those are the most important. We did so many migrations in the past 30 years and the only ones that went ok were the ones that held to these rules. If you don't, you are rapidly stuck in a lot of pain and probably you won't be able to get out.
110% this. Resist the urge to make changes until everything is moved over. Any system 'enhancements' may also be viewed as bugs/defects, and reduces trust, requiring lengthier validation.
> Don't get tempted into doing refactorings as you go.
I would say those are the most important. We did so many migrations in the past 30 years and the only ones that went ok were the ones that held to these rules. If you don't, you are rapidly stuck in a lot of pain and probably you won't be able to get out.