One of the most important fields that I utilise when creating and processing OmniFocus actions is the Notes field. It just does so much more than it's name suggests!
Let's look at some examples of how this field is used in my workflows every single day:
Timestamping with TextExpander
I guess the most common use I have for the Notes field is timestamping any actions that I take so that I can retrospectively look back at any progress that has been made. Invariably, this is most common when I am Waiting For actions from others and the timestamp is to inform me of when contact was made.
My time stamp has the following format - yyyy-mm-dd hh:mm and can be typed in manually if you don't use a built-in expansion tool like TextExpander, however it cannot be argued that it isn't easier to automatically fill this out with just a few keys. My abbreviation is xxdts and the output is configured as %Y-%m-%d %H.%M
Links to Evernote Reference Material
As much as I have tried to move away from Evernote and adopt one unified system for all research tools, I have to admit, it is great for grabbing content on the move. I do a lot of research when I am commuting and I am yet to find something as efficient as the Evernote sharing extension on iOS for Pocket and Safari articles. I still import these into DEVONThink Pro Office (blog post to follow) so that I can follow my principle of having one efficient Search domain for all of my files and project reference materials.
When I need to refer to an Evernote note directly from an OmniFocus action, I first need to copy the link to the note itself. This is achieved by right-clicking the note and selecting Copy Note Link. Paste this into your Notes field in your OmniFocus action and you have a direct link between the two, making navigation and app switching a breeze, especially when you have split screen enabled between the two applications.
Direct Links to Finder Documents
I have several actions in OmniFocus that require me to access or update certain files. These could be Numbers sheets, image files, bookmarks. The Notes field is a great place to place shortcuts to these documents so that you don't have to use Spotlight/Alfred/Launchbar etc to find the file that you need to refer to.
To grab the link, you can Ctrl+click on the file and select Copy or Copy Path - URL and then paste from the clipboard straight into Notes. Or, simply drag and drop the file from Finder directly in - whatever is easier for the situation you find yourself in.
Now, it's important to know the distinction between adding links to documents and actually embedding them. The options above will link to an existing file, however when you sync your database, then you will not be able to view those files on your iOS devices. Well, that makes perfect sense - OS X and iOS use different file systems. By embedding attachments into the Notes field, they will be synchronised with the OmniSync server and able to be pulled down on your mobile device.
To attach a file, Ctrl+click on the action that you wish to attach the file to and select Attach File
A standard Finder window will open and allow you to navigate to the file that you wish to attach. Select it and boom, you're able to look at that file on multiple devices (as long as you have an application able to open it of course!)
Those are my standard uses for the Notes field in OmniFocus. There are lots more out there I'm sure, I just haven't gotten around to finding them out yet but please, feel free to contact me with suggestions and I'll share them out.