When I work in Houdini, I like using a certain standard for different node types (i.e. controllers and OUT null nodes). These are tools I wrote to change the formatting of nodes with hotkeys or a shelf button rather than manually edit the node each time. If the desired node name is already taken, a counter is appended. These scripts can be customized based on the node color and name the user would like to use. I am currently working on a modification to these scripts to allow a user who is less familiar with Python to use them as desired. These scripts can be added as shelf tools and saved as a hotkeys. See the project on Github.
I like my OUT nulls to be red and have the prefix OUT. I like the shape to be "pointy". So, I prepend "OUT_" to the node name and change the visuals. If "OUT_" is already part of the node name, it is not prepended again.
Similar to the previous, this script changes the name of the node to "CTRL" (or adds a counter if that name is already taken) and alters the color and shape.