How can I get apt to use a mirror close to me, or choose a faster mirror?
apt-get now supports a 'mirror' method that will automatically select a good mirror based on your location. Putting:
deb mirror://mirrors.ubuntu.com/mirrors.txt precise main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise-updates main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise-backports main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise-security main restricted universe multiverse
on the top in your /etc/apt/sources.list file should be all that is needed to make it automatically pick a mirror for you based on your geographical location.
Lucid (10.04), Maverick (10.10), Natty (11.04), And Oneiric (11.10) users can replace precise with the appropriate name.
I've always gone with the 'select best server' GUI tool: from Ubuntu Software Center, go to Edit -> Software Sources in the menu. (You can also do this from the Preferences for Synaptic or the Update Manager.)
Under the Ubuntu Software tab there's a drop-down next to "Download from:" If you select "Other..." you'll get a button that says "Select Best Server"; clicking on it gets Ubuntu to run some tests to see what mirror will give the best download speed.
I can't comment on whether this is better or worse than the method you found for yourself. Perhaps someone with some expertise on the issue can comment!
Here are some screenshots for the graphical method, as Jorge suggested:
Open the Ubuntu Software Center, click on Edit in the global menu, and go to 'Software Sources...'
Click on the drop-down menu next to 'Download From' and select 'Other...'
Click on Select Best Server
The best server is highlighted. Click Choose Server and you're done!
The Geographic location does not always give the best mirror. For example, I live in BC Canada, and most who are in this province should find a mirror in BC, California, or any Pacific state, maybe even Arizona.
However, here in the north my ISP (unlike the phone company) has only one fiber line out of this city, and it goes straight to Calgary (1000km east of here) where it plugs a NEX shared with the line to ucalgary, where they have a lovely debian and ubuntu and who-knows-what-else mirror. It seems the university has the same ISP as I, and so transfer rates are measured in megabytes per second, as opposed to the 50-100 kilobytes per second I get from a default mirror.
So. I recommend knowing your local internet network topology. Pretty things such as Network Exchanges can make for a fast connection to specific places. Staying on your ISP's network can bypass some speed throttles you might otherwise have to the outside world.
Thanks to the post regarding the GUI tool to change this, I found that mirror and set it as default. Good show for this topic!