Synchronizing between Macs and mobile devices
OmniFocus version 1.5 introduces the ability to synchronize your database with a server or a disk, so that all of your Macs, and your iPhone or iPod touch, will stay up to date.
To get to the Sync preferences, just choose Preferences from the OmniFocus menu, then click the Sync button.
By default, OmniFocus is set to sync with Nothing — in this case, the database in your Library folder is the only one that matters.
Step 1: Archive old data
If you have been using OmniFocus for more than a couple of months, you may want to archive your old, unused items before setting up synchronization. Choose Move Old Data to Archive from the File menu; your database will be slimmer and faster to sync, especially on iPhone or iPod touch.
Step 2: Choose a sync method
In order to synchronize, you need to keep a “server” or “sync” copy of your database somewhere, and let OmniFocus check up on it periodically. There are several types of places you can keep the sync copy, each represented by a button on the Sync pane:
MobileMe — This service from Apple includes iDisk online file storage; if you have a subscription, this is the easiest way to put your OmniFocus database where all of your Macs and devices can synchronize with it over the Internet.
Bonjour — This is a very simple way to let Macs and devices on your local network discover and sync with a copy of your OmniFocus database. As it doesn't require special setup or a subscription to a service, this is the simplest way to synchronize Macs or devices locally.
Omni Sync — Omni's own Omni Sync Server. Store your document as a back up or sync with OmniFocus on other devices over the air. Tap the sign up button to create an account or, if you have one already, enter your username.
Disk — Anything that you can mount and edit as a disk in Finder, such as a portable USB drive, a Time Capsule on your local network, or a file server that you access over the internet, can be used to synchronize your OmniFocus database. Note that iPhone and iPod touch can’t mount disks over the network like a Mac can, so this sync method won’t work with it.
Advanced (WebDAV) — This is a type of server for sharing files on the web, offered by some hosting providers. Check with your hosting provider to find out whether you can set up your own WebDAV space. Be aware that providers which don’t fully comply with the WebDAV standard may not work properly.
Step 3: Choose a sync location 
MobileMe — If your MobileMe account information is already set up in System Preferences, then your Location field is already filled in. You can add a folder name to the end of the URL if you want to keep your database somewhere other than the top level of your iDisk.
Bonjour — Click Keep the sync database on this Mac, then enter a password to protect your database. OmniFocus then makes a sync copy of your database available to other Macs and devices on your network.
Omni Sync — Create a login with the sign up button, then enter you username. Once you've entered you username, use the account info button to visit sync.omnigroup.com to manage your account settings or grab a backup.
Disk — When you choose to synchronize to a disk, a sheet appears for you to choose a location. Make sure the disk is mounted, browse to the location on the disk you want to use, and then click the Set Sync Location button.
Advanced (WebDAV) — Enter your WebDAV address (such as www.example.com—webdav) in the Location field. If your provider supports it, you can use https for a semblance of security while transmitting your data; otherwise, ordinary http also works.
Step 4: Sync 
Click the Sync Now button to start your first sync. Since you don’t have a sync database yet, this first sync will consist of creating one and copying all of your OmniFocus data into it.
Step 5: Set up other Macs and devices 
Once you’ve fully synchronized your database to the server for the first time, you’re ready to tell your other Macs and portable devices about it.
Setting up another Mac — Follow steps 1, 2, and 3 again on that Mac, using the same settings. (If you are using Bonjour, click Connect to an existing sync database and select the Mac that you set up before.) When you synchronize that Mac, it finds the existing database on the server.
Setting up an iPhone, iPod touch, or iPad — OmniFocus is available for the iPhone, iPod touch, and iPad from the App Store. If your device is on the same wireless network as your Mac, you can open OmniFocus on that device and choose to get the sync settings from your Mac by name. Otherwise, click the Send Settings button on your Mac’s OmniFocus Sync preferences pane to email a special link to yourself. (If you don't see these settings, click the disclosure triangle on the bottom-left, next to the "OmniFocus for iOS..." text, to show those options.) Open the email on your mobile device and tap the link; OmniFocus does the rest.
Step 6: Stay in sync 
One minute after you make any change, OmniFocus automatically synchronizes with the server. With Bonjour sync, whenever you make a change on one client, any other clients that are awake and connected to the network are notified right away. Even if you don’t change anything, OmniFocus syncs once an hour. You can also manually sync by choosing Synchronize with Server from the File menu, or by clicking the Sync toolbar button. As long as OmniFocus synchronization is enabled on all of your computers and handheld devices, and they can all reach the database on the server, they will all be up to date with one another.