2. How can I use more than one Write node and render in different orders?
I really often have multiple Write nodes in my trees and sometimes, especially when doing some precomps, the processing order is important. In Nuke you have the possibility to set your rendering order really easy. Let’s assume you have a tree like mine in the image below.

You would want to render out your Write1 node in advance, then the filters are applied and then the Write2 node will be executed. To set this up go into your Write nodes and check the settings in the render order parameter. For the Write1 node it should be set to 1, which is the standard, and in your Write2 node you change your order to 2. You will notice that in the DAG your node will show you a small 2 , indicating that the order was changed.

When you now Execute your script Nuke will recognize the Write orders and render appropriate.

3. Now how can I render the script outside Nuke ?
I got this question a few weeks ago. I for my part nearly always use the terminal to render my Nuke scripts. First I noticed that the rendering process was way faster, and second I got used to it, because especially in nuke4.6 when doing some retiming, the render process was not successful inside the app, and rendering in the terminal was sort of a workaround. So after saving your script you can close Nuke and go to your terminal and type in the following:
nuke -x yourscript.nk 0,100
-> 0,100 is the timerange you want to render, so change this to what ever timerange you want to execute. You should also be aware, that you have to type in the whole path to your script. And if you have not set an alias to Nuke, you also have to type in the path like in the image below.

If you have multiple Write nodes in your script and only want to execute one of these, you can type in :
nuke -x Write1 yourscript.nk 0,100
this command will execute the Write1 node only. To learn more about this, type in nuke -h and you will get a list of all available commands.

So I hope this tips have been useful, and hope you check back soon ! !