Some common tips for everyday use:

If network manager does not connect at restart:

You first need to know your network interface name. There are several ways of getting it. I will only tell the command line way:

sudo /etc/init.d/networking restart

It will throw a result like this:
* Reconfiguring network interfaces...
Ignoring unknown interface eth0=eth0.

This means your network interface name is eth0

(above way is not the best way but will work. If you are one of those detail oriented pesky little prim and proper types, do this to see all info about the network devices: lshw -C network and look for the interface name under *network- in the field "logical name:". By the way, lshw command will still show you nothing if the network manager could not "detect/connect" the network card. So, you still have no other way than the networking restart way shown above)

now do: sudo ifconfig eth0 up

If your network interface had a name other than eth0, use that instead of eth0 in the previous command.

To go offline, do: sudo ifconfig eth0 down

(again, if your network interface had a name other than eth0, use that instead of eth0 in the previous command)

When the GUI Update Manager crashes:

This oftentimes happens. When it does, this is the equivalent way:

sudo apt-get update

followed by

sudo apt-get upgrade

Sometimes, neither the Synaptic GUI nor the command line work (we get the dreaded Segmentation fault error). Then do this:

sudo rm /var/cache/apt/*.bin

Then run the update and commands again. This should work now.

Setup Samba to share files across Windows/Mac computers:

First step, to determine if you have Samba aleady installed:

run this command to check if you have samba:

dpkg -s samba

If it says, you have samba installed (get rid of it and do a re-install)

to uninstall (if you had samba) do this...but skip this step if you dont have it:

sudo apt-get purge samba

then do a samba install:

sudo apt-get install samba

you should now be able to share folders across windows/mac computers.

However, if your Windows/Mac computers are part of a network, you will need to edit samba config file to add that workgroup name. For example, lets assume the workgroup name is ANDROMEDA.

Now do this:

gksudo gedit /etc/samba/smb.conf

search for "workgroup =" (without the quotes)

you should see a line like this: workgroup = WORKGROUP

replace WORKGROUP with ANDROMEDA

save and close gedit. Now it should work.

Setup Flash on Chromium.

I noticed that the flash plugin I downloaded directly from adobe used to crash my chromium browser every 15 mins. It was ruining all browsing experience to the point I started rating IE6(via wine) better than Chromium (IE6 is slow but does not crash like a bucking bronco). Anyways, I decided to give chromium one last try. So, I uninstalled the existing flash plugin via Synaptic Package Manager GUI.

Then I did this:

sudo apt-get install flashplugin-nonfree

after this, do this:

sudo cp /usr/lib/flashplugin-installer/libflashplayer.so /usr/lib/chromium-browser/plugins

Now you can launch the chromium browser through Terminal like this:

$>chromium-browser --enable-plugins

To enhance the browsing experience, add the chromium icon to the quick launch bar like this:

Applications->Internet->Chromium Browser and right click it, add to panel. Right click the new chromium icon and then add the following command where it says command:

chromium-browser --enable-plugins

Well, chromium now looks to be more stable (been 15 mins and still not crashed). Will keep my fingers crossed. Amen!