1/ You can turn the scroll bars back on — In System Preferences, which is probably in the Dock (grey cogwheels) and if it’s not, it’s always available from the Apple menu) on the General tab, you can turn ‘Show scroll bars’ to ‘Always,’ and your scroll bars will always be visible. Then you’ll always know if a field is scrollable.
2/ Safari Favorites (sic) — OS X by default now hides the favourites bar in Safari. To turn them back on, just choose View>Show Favorites Bar.
3/ Change the Dock appearance — The so-called stacks that appear on the right-side of the Dock (or at the bottom if you have the Dock on the side, as I do, above) can be confusing. Folders in the Dock show their contents rather than a folder icon, which means the way they look changes when something new is added to the folder it’s linked to (this is in the area to the right or bottom, between the Trash and the vertical divider line, which is the area for files and folders rather than apps as in the rest go the Dock). To switch this, right- or Control-click on one of those Dock folder icons on the right or bottom, and choose ‘Display as…Folder’ from the popout menu.
4/ Add descriptive text to Mail’s toolbar — To make Mail’s icons more understandable, right- or Control-click on Mail’s toolbar (the grey strip across the top of the window) and choose ‘Icon and Text’ from the menu that’ll appear, and those icons will actually mean something.
5/ Bluetooth’s secret Debug menu — If you’re having issues with a connected peripheral device like a Bluetooth keyboard or mouse, there’s a special menu option buried beneath the Bluetooth symbol near the top-right of your screen. (If you’re missing that icon, open System Preferences, select the Bluetooth tab and check ‘Show Bluetooth in menu bar’.)
Once you can see it at top right of your screen, hold down the Shift and the Option keys on your keyboard at the same time, then click on the icon. A Debug menu appears. This contains a few very useful choices: Reset the Bluetooth module” completely wipes all of the hardware module’s settings. Enable Bluetooth logging creates a new log file (viewable within Applications > Utilities > Console) that you can check out if you’re great at parsing log-speak.
The fourth option, Remove all devices, would be great to know about if you were moving, say, a mouse and keyboard to a new workstation, as they’d then be easy to pair with the new Mac.
The third choice, Factory reset all connected Apple devices, forces your Apple stuff back to factory settings, which is an incredible troubleshooting step if you’ve already tried things like turning the devices off and on again, unpairing and re-pairing, deleting Bluetooth preferences, resetting the SMC, and so on. Your Mac will give you a somewhat ambiguous (but still scary!) warning if you attempt to do this:
Extra: there’s one more quick trick. If you hold down Shift-Option, click on the Bluetooth menu, and then select one of your connected devices, you can choose to do a factory reset on that device only.
(Be aware that if you choose to do a factory reset on anything, you’ll have to re-pair it to your Mac, so here are Apple’s instructions on how you do so. But hopefully, whatever big bad Bluetooth problems you were having will be resolved after that, and nothing will have to get thrown at the wall or set on fire or stomped into pieces out of anger! A girl can dream.)
(These Bluetooth tips via Mac Observer.)