Make it easier, and quicker to get to the start When teaching I often have pupils struggle in the first few minutes. When they are setting the computer up, ready to start work. They often have to follow lengthy instructions, that I print on paper, of mostly screen snips (So this also takes a long time to prepare).
What can I do to make this easier for pupils?
For example
I have had a lesson where I have had detailed instructions on setting up Python/Idle: Starting the editor, finding starter code, they contain many screen shots. This took me a long time to prepare, and is not easy for the pupils. They are not productive at the start of the lesson, and get demotivated.
They need to get to:

starter code copied to there personal folder.
idle started and on one side of the screen.
code loaded into idle.
code run.
output window on other side of screen.

Common errors:

running code without idle (so they can not edit it).
running my copy of the code (so they can not edit it).
overlapping windows (so they are frustrated that they can not see, and spend a lot of time moving windows). (This one can be solved with better digital literacy, at the start, or a bit at the start of each lesson.)

I have had the same problems when teaching spreadsheets, and am anticipating it with web design. I was hoping to use the brackets editor. The start state would be.

starter code copied to there personal folder.
brackets started and on one side of the screen.
root folder loaded into brackets.
live preview started.
browser (output) window on other side of screen.


The computers are the schools desktop computers. Unfortunately they are running MS-Windows.
This question seems like a minefield. The obvious answer is "Don't Do That." No group of people, students or professionals, is going to interpret two pages of instructions in exactly the way the writer intends. It isn't going to happen. They will misinterpret individual steps, skip steps trying to optimize, crash the machine when they don't have a conceptual idea of the goal, etc. 

In the first place, your instructions may be clear to you, but until you vet them with others they won't be clear to most other people. This is why textbooks have editors and why authors re-write continuously. 

There are, however, a few things you can do. 


You give one answer yourself here - Automate It. In fact you can improve the automation if you distribute the code yourself and execute it yourself from a central server. Automation isn't foolproof, however, as some of the machines in the lab will, perhaps, have different initialization parameters baked in that defeat your script. 
Another possible solution is to decide on a standard startup process and configuration that you always use. The students can learn this and only struggle with it for a day (or week, ...). 
Make the startup description shorter. As short as possible. Then a bit shorter. Vet it with someone else who is skeptical about it. Re-write it using their feedback. 


But even then, you will fail. Different students will interpret your writing differently. That is pretty much guaranteed. Your writing won't be perfect. Neither will their reading (and understanding) be perfect. If you need different instructions each day and they can't be vetted, I wish you the luck you aren't likely to have. 

You can do more, perhaps. 


If you can live with students always working in pairs at the machines, then you have cut the interpretation problem roughly in half, maybe more. Only half as many machines need to be set up and there are two minds working on each machine. (Of course they could disagree making the problem harder, but usually this helps.)
If you can manage to have an assistant wander around the room helping the students with the most trouble it can help, though pairing is better. (Paired programming has been shown to be more efficient and require less intervention by the teacher, but that is not quite the same problem you pose here. Students working alone get stuck and wait unproductively for assistance. Pairs work it out.)


There is one special difficulty that you need to address. Minutely detailed and extremely precise descriptions are often especially hard to follow if the person trying to carry them out has no overall context or goal that they understand. The reader likely has no way to check that each step was faithfully executed in the correct order. Any glitch will cause a serious problem for that person. With a group of individuals, there will be many independent problems simultaneously. Whack A Mole.