Handoff is a highly touted new feature of iOS 8 and OS X Yosemite that allows for seamless continuity between your devices. For example, if you start an email on your iPad, Handoff will allow you to pass the draft to your iMac and continue writing it there. Handoff will also work with Safari, Notes, Keynote, Numbers, Contacts, Calendar, Pages, Messages and Reminders, and it is open to developers as well, so it will soon work with third party apps.
If you've been having trouble setting up Handoff, you aren't alone; there has been a lot of confusion about it over the past several days. Here are a few potential reasons for your frustration:
Bluetooth 4.0 (BT LE) - Handoff requires Bluetooth 4.0 to be enabled on both devices. You can check what iPhones and iPads have Bluetooth 4.0 here. Most recent Macs should have it, but if you are unsure it's easy to find out:
1. Go to your menu (top left of your screen) and click "About this Mac."
2. A window pops up showing you your OS X version and some other details. At the bottom of the window is a "System Report" button. Click on it.
3. A new window pops up with a list of options to click on in the left panel. Under "Hardware," click on "Bluetooth." The information in the right panel will change.
4. In the right panel, look for "Handoff Supported." If it says no, you don't have Bluetooth 4.0. For further verification you can scroll down to "LMP Version." If you have Bluetooth 4.0 the LMP version will be "ox6."
If you have Bluetooth 4.0 you're in good shape. You don't have to pair your devices. Just make sure Bluetooth is enabled on both and make sure they are in range of each other (within about 30 feet). On a side note, if you've been trying to pair and have been frustrated by that, your Mac will only pair with your iPhone if the phone's hotspot is turned on, which will allow your Mac to use your phone's data connection.
iCloud - Both devices need to be signed into iCloud in order to use Handoff. From the iPhone and iPad go to Settings -> iCloud and sign in if you aren't already. From your Mac go to System Preferences -> iCloud to sign in.
Wi-Fi - Both devices need to be connected to the same Wi-Fi network.
Turn on Handoff - A third factor that may have slipped your mind is activating Handoff. On your iPhone or iPad go to Settings -> General -> Handoff & Suggested Apps and use the Handoff toggle to turn it on. On the Mac, go to System Preferences -> General. If you have Bluetooth 4.0 you will see a checkbox near the bottom of the window for "Allow Handoff between this Mac and your iCloud devices." Make sure that is checked off.
And, as always, it's a good idea to have the latest iOS and OS X versions, as Apple is always fixing various bugs that may have been giving you problems.
Hopefully this clears up a few issues. If not, or if you have more suggestions, let us know.