Maybe less of a hint, and more of a "I didn't know you could do that!"
If you have connected to a remote Mac using Screen Sharing and don't have a mounted disk, then you can still copy between the two Macs via drag and drop.
Basically, you take a file from the local Finder and drag it to a window of the remote Finder. This will automatically initiate a copy. The reverse is also true. A little experimenting shows numerous applications can act as source, but in all cases a Finder window needs to be the final destination.
[crarko adds: I've done this for ages using things other than Apple's built-in Screen Sharing program, so I don't know when this became available. Did it come along with AirDrop? The full Remote Desktop program has done this since the beginning.]
When re-installing Mountain Lion from the Recovery Partition, the installer needs to check installation eligibility with Apple's servers. If your computer needs to access the Internet through a proxy server for whatever reason, the installer won't pick up on this; it will attempt to make a direct connection, fail, and tell you to contact AppleCare.
As per my earlier hint (10.7: Get the Lion installer to work behind a proxy server), you could simply use the networksetup command in Terminal to get around this. However, as of 10.8 Apple's software download servers appear to require additional checks to verify machine eligibility which - if you're behind a squid proxy server - may require additional configuration changes to squid itself in order for it to work. You may therefore need help from your network administrator for that part.
First thing I do when I get a new system is to redirect downloads from ~/Downloads to /tmp.
The advantage with this adjustment is that in /tmp files older than a week is automatically deleted (and at every restart). Almost all files I download don't need to be stored, for example:
1. Installers. Run the installer (or dmg) from /tmp and then forget about it and it is automatically deleted within a couple of days.
2. PDFs I just want to read (or possibly print) once.
3. Templates, e.g. expense reports and similar (typically .doc or .xls). I download it, fill it in, generate a pdf and e-mail to the appropriate recipient. No need to keep the original template.
4. Torrents. Download the torrent, add it to your torrent client and then there is no need to keep the original torrent file around anymore. Besides, a lot of the files I download using torrents I just "use" them once so they can be also be downloaded to the same folder as the torrent is stored in, that is /tmp.
If I ever need a file that has been deleted from /tmp I just go to the browsers download history and download it again. Happens me maybe once or twice/year. So much easier than trying to find a file among hundreds of randomly named files in the Download folder.
I also always drag /tmp to the sidebar in the Finder and use it for - ta-da - temporary storage of files I work with briefly. Then I never need to cleanup my Downloads or Documents folder ending up in situations where "Hmm, what is this six months old file? Should I keep it or not?". If I put it in /tmp I know that
The very few downloads I want to store more permanently I just select Save as… when I click the download link and directly store them where they are supposed to go.
I just wished I could change the download folder for applications such as Bluetooth receive file, Skype, Mail.app etc. They still fill up my download folder in a very useless way.
Mavericks introduced several bugs into the Finder. One of them is that in List View, the Finder frequently loses track of the column widths, and makes the Name column so wide that the other columns aren't visible unless one scrolls the window horizontally.
The following Applescript resets the column widths to something sensible. It uses a couple kludges to work around some *other* Finder bugs that Mavericks introduced.
-- Reset the width of the Finder's Name column to something sensible.
tell application "Finder"
set thisFolder to target of front Finder window
set the current view of front Finder window to list view
-- In previous versions of OS X, the next line would tell the Finder to set the width
-- to exactly 300. In Mavericks, the Finder uses it as a *minimum* width.
set width of column id name column of list view options of Finder window 1 to 300
-- The following kludge is necessary to get the changes to "take". I got it from
-- Dr. Drang at www.leancrew.com/all-this/2013/10/quick-switch-to-big-finder-icons
close front Finder window
Mavericks now considers each monitor a "Space". As a result, apps launch and have their menu bar in whichever monitor they were launched from. However, it's easy to assign apps to each monitor. Here's how:
First, you need to create an additional space in Mission Control. You can add it to either monitor.
Having done that, then when you right-click on an app in the Dock, you will see the option to assign the app to All Desktops, Desktop on Display 1, Desktop on Display 2.
If you are a heavy user of Spaces with multiple displays, then you have likely found that the new "full screen improvements" in Mavericks are a giant leap backwards. To get the old behavior back, just go to Mission Control in the System Preferences and uncheck the box labeled "Displays have separate Spaces."