I have been using OmniFocus now since it first came out on the market and GTD for even longer. This is what I have learned overt the years on how to use OF and GTD. I hope it will save others some time!
Use lot’s of projects
I suggest being generous with your definition of projects. The beauty of projects is that you can review them individually and you can put them on hold.
Have a flat & simple structure
Having lots of projects may require somewhat more folder structure but try to keep it as flat as you can. It’s a lot of work moving projects into the correct folders all the time. Instead put projects on hold and your system will still be pretty tidy.
Everything you see is on the weekly horizon
Create your week plan by putting everything else on-hold so you don’t have to see that. Use the review feature to bring them back to life.
Avoid Single Action Lists (SAL) as best you can because they tend to become dumping grounds for tasks that are actually projects. You can cheat and assign individual tasks to an on-hold context but then you loose its real context.
Keep contexts to a minimum
• Avoid having lots of contexts because you need to remember all your contexts so you know which one to file a new task under. Besides, being granular with contexts will make you run into gray zones - this or that context questions. Have only a few contexts and use the on-hold technique to keep them tidy. This is why tags are useless. If you have 25 tags - how are you going to remember them all - your system will be inconsistent in no time. This is also why allowing only a single context on a task is brilliant - it requires you to have broad contexts and a simple system that is easy to remember.
• A context must always be useful! Having a “read” and “write” context for example isn’t at all useful, to me at least.
What if you have a task that requires you to do both? It’s all just “work” to me. I simply need a quite moment to take it on. Don’t use contexts to just divide up large amount of tasks - again, use the on-hold technique.
Flagged = intend to do today
Everything that isn’t on-hold is on the ”weekly list”. In the morning flag stuff you want to work on today. Use a flagged perspective on the iPhone widget to quickly check important stuff.
Make it easy to capture
Use the Siri integration to capture open loops into your inbox. It works great (costs little effort) but you need to process that inbox daily because the input is pretty crude.
System drift is normal - learn to deal with it
If your system is “drifting” - you haven’t had time to organise and clean it. Use flags to pick out the important stuff and work out of a flagged view. Tidy things when you have time.
Review date = tickler
So daily review of inbox and flagged view. At least weekly review using the OF review system. Use the ”next review” date to get projects to pop up on your radar when you want them to.
Learn you own system and keep it fresh
If you have a massive amount of inbox items, try to do a proper review first before tending to the inbox. It will remind you of your already existing projects and folder structure and you will file inbox items more correctly after that.
Hard dates = hard
Events and meetings go into your calendar. Use only due dates for things that have a real deadline - avoid using it for artificial deadlines - ”I would like to get this done by friday”. You will go blind to due dates and pushing due dates around is a lot of work.
Defer = later this week
Use the ”Defer until” if you have a task that you can’t/won’t do anything about until later in the week. For example, you ask Bob to create a report. You need to remember to follow up in a few days that he actually did: ”Follow up that Bob actually created the report”. Flag and defer that a couple of days and it will popup on your today list.
Use people contexts
These are my most useful contexts. For example, I have a 1 on 1 meeting with the CEO once a week and I collect all things to discuss with him during the week in his context as they pop up. Then when the time comes I just bring up that context and we deal with all those questions at once. It saves a lot of time. I also have a ”Team” context. I collect things I want to discuss with the whole team there. I also use people contexts for delegation.
I hope this helps!