When confronted with all the possibilities that tagging opens up it is very tempting, nay nigh on impossible not to go completely overboard. The first big mistake I made was to just tag everything I had at quite a granular level, but as basically a lazy person this soon became way too much of an overhead given the benefits, so after seeing a remark from David Sparks in the OF slack channel about planning an OmniFocus workflow with mind maps I decided to pull the whole system apart and give it a go.
This is where I am at the moment..
I am a self employed designer/developer working at home so I have a lot of "blurring" when it comes to areas of responsibility and long lists I find demotivational, so try to break stuff down as best I can. I also have become quite "zen" with tags, only applying tags that either produce the perspectives I need, or to block certain things together, e-mail, calls and locations being the main ones.
My "[Today] Routine" perspective handles all my business and client admin, repeating stuff like weekly accounts, and filing, monthly server reviews, trips to check forums etc etc. We (my partner and I) also handle tweet accounts and blog writing for clients which go in here as well. Basically this apart from an evening wind down task should be clear by midday.
My "[Today] Work" perspective houses the one off customer support stuff as well as things from the between 4 and 8 design/SEO projects I probably have running. This is the big stuff and gets worked on throughout the day, but I try to keep this to afternoons where I can.
What I have found that works well is where something is going to take more than a day or gets put down in favour of something urgent assigning a "Working on" tag allows me to hide it from the Work perspective and keep it in the "Still Working on" one, colour coded green for go so I have a visual clue to keep checking it. This tag is also the "blessed" tag (the one which can appear in the built in forecast perspective) on the iPad.
To be honest this was a bit of a steal from 2Do which gives this option in its Today view.
"[Today] Personal" is pretty self explanatory I try not to check this during the day, unless I have a spare few minutes or need a break, I keep automated notifications of new saved reading items or things to check out here so I can dive in and read something, otherwise I run through this in the evening.
The "Domains and Hosting" are just date ordered lists of all clients domain renewals and pre hosting invoice mails I need to send which also appear in "[Today] Work" as they fall due. "Payments" is what I need to pay out, it holds way to much but that's modern life I guess.
The only other non standard one is all my Design/SEO projects are set to be reviewed daily (another idea from the OF slack channel this time from "heyscottyj")this gives me a quick way to check on progress and keep them ticking over and therefore me paid.
The glue which holds this together is my "morning review" and a "wind down" set of repeating tasks to check all these perspectives as well emails, appts etc which I do at 6am over coffee or 6pm over you guessed it coffee. in the process of writing this I have also introduced the "Upcoming" perspective which shows everything deferred or due today and in the future (filtered on business tasks only), this gives me a pretty good overview of the small tasks coming up which eat time if your not careful.
Tagging I have kept simple, basically just to make the perspectives work, with the following "Routines Work", "Routines Client", "Routines Personal", these are powering the "[Today] Routine" perspective.
Next is "E-mails", "Calls", "Money". The first two just to block tasks during the day, the last to power the Payments perspective. I have a couple of location based tags, a Waiting", and of course the "Waiting for" tag discussed above. I am really trying to keep tags to the minimum the temptation of course is to go nuts with them as I have said.
So far this system seems to suit my way of working and my particular needs. The tagging, plus the vastly improved filters in perspectives open a lot of opportunities to experiment and I would advise anyone to do just that. If this post helps, great, but I would really suggest whatever you do, you make any system your own, not someone else's, and OmniFocus 3 really allows you to do just that.