Here’s the step:
1. When you plug Huawei E220/E270 modem, a notification will appear. Then click configure button.

2. Next press forward.

3. Select your country and your operator, usually it’s automatically detected and automatically configured.

4. Then click apply.

Then it’s finish. You can connect now. Just click on network manager and then connect.

If you want to edit the setting, just go to:
System -> Preferences -> Network Configuration
Then select “Mobile Broadband” tab to edit or add a new connection.

There you can edit the setting of your username, password, APN etc.

Configuration:
OS: Ubuntu (Gutsy Gibbon)
Modem: Maestro Lite 100 GPRS/GSM Modem
Connection: /dev/ttyUSB0

Here’s the configuration in /etc/wvdial.conf, I’m using AXIS simcard (you can edit your own username, password and access point.

[Dialer Defaults]
Username = axis
Password = 123456
Phone = *99***1#
Init2 = AT&F
Init3 = AT+CGDCONT=1,"IP","axis","0.0.0.0",0,0
Stupid Mode = 1
Inherits = Modem1
New PPPD = yes
Dial Command = ATDT
ISDN = 0
Modem Type = USB Modem

[Modem1]
Modem = /dev/ttyUSB0
Baud = 9600
SetVolume = 0
Dial Command = ATDT
Init1 = ATZ
FlowControl = crtscts


After successfully dial up, you will be able to browse the web. Here’s some log when connect:

iqbalir@unknown-localhost:/$ sudo wvdial
WvDial< *1>: WvDial: Internet dialer version 1.56
WvModem< *1>: Cannot get information for serial port.
WvDial< *1>: Initializing modem.
WvDial< *1>: Sending: ATZ
WvDial Modem< *1>: ATZ
WvDial Modem< *1>: OK
WvDial< *1>: Sending: AT&F
WvDial Modem< *1>: AT&F
WvDial Modem< *1>: OK
WvDial< *1>: Sending: AT+CGDCONT=1,"IP","axis","0.0.0.0",0,0
WvDial Modem< *1>: AT+CGDCONT=1,"IP","axis","0.0.0.0",0,0
WvDial Modem< *1>: OK
WvDial< *1>: Modem initialized.
WvDial< *1>: Sending: ATDT*99***1#
WvDial< *1>: Waiting for carrier.
WvDial Modem< *1>: ATDT*99***1#
WvDial Modem< *1>: CONNECT 9600
WvDial Modem< *1>: ~[7f]}#@!}!}!} }6}!}$}%\}"}&} } } } }'}"}(}"}#}$@#&4~
WvDial< *1>: Carrier detected. Starting PPP immediately.
WvDial: Starting pppd at Wed May 14 21:20:46 2008
WvDial: Pid of pppd: 6603
WvDial< *1>: Using interface ppp0
WvDial< *1>: local IP address 10.83.211.127
WvDial< *1>: remote IP address 192.168.111.111
WvDial< *1>: primary DNS address 203.78.115.215
WvDial< *1>: secondary DNS address 203.78.115.222

Another modem:
If you are using Huawei E220 HSDPA Modem (Some time I use this one also), you can find “how to” here.