Now it is really easy to use any MP3 file as ringtone on almost all cell phones, you just need to transfer the song to the phone and make it your default ring tone.

But there are two problems with this, at least for me.

1. My phone does not have enough memory to have too much songs
2. Almost all songs start with low volume, and when I finally hear it, the call was droped

Well, to solve that, you need to edit the mp3 file and transfer to the phone only the part you want to use as ringtone, and the tool for that is: Audacity, to install it on Debian just run:

apt-get install audacity

Once installed, open your mp3 file with it, and select the part you want to use.

Now to export it as mp3, we need the libmp3lame.so library, on Debian you need to compile it from the source, so download it to /usr/src/lame directory, these are the instructions to install it:

cd /usr/src/lame

tar xvzf lame-3.97.tar.gz

Change to the version you have downloaded

./configure

make && make install

Now on audacity select from the menu:

File -> Export As MP3

Audacity will ask (only for the first time) the location of the library libmp3lame.so so select:

/usr/local/lib/libmp3lame.so

and there you go, you are now ready to transfer ringtone to the phone, and enjoy it.