If you are using Ubuntu Dapper Drake, you could press CTRL+SHIFT and then the unicode for special characters so you didn't have to copy and paste them from the Character palette every time you wanted to use them.
If you are using Edgy this will not work any more here is simple tip how to use Special Characters.You need to use compose key
If you want to enable compose key go to System ---> Preferences ---> Keyboard
Once it opens you should see the following screen
Now you need to select Layout Options tab from the above screen
Now you need to expand on Compose key position
Choose Right-Win key is compose, click Close.
To use it, hold the Compose key down and then type in the characters you want to mash together.For Example check the following ones
RightWin + C + = produces €
RightWin + = + C produces €
RightWin + C + O produces ©
RightWin + O + C produces ©
RightWin + a + ‘ produces á
Another option is you can proceed the following procedure
If you can't make fractions like ½ with the above solution you can fix that using the following procedure
you need to edit the /etc/environment file using the following command
sudo vi /etc/environment
add the following line
Save the file and exit
Now you need to copy this file to your home directory
cp /usr/share/X11/locale/en_US.UTF-8/Compose ~/.XCompose
This will give you a more complete character set.For example that your keyboard doesn't have a tilde (~). You can change the lines that require entering a tilde so that a simple "t" (or whatever you like) will work. Just don't use a key combination that's already in use.