Everyone with experience of having planned a wedding will vouch for the fact that a creating a comprehensive guest list was a difficult task. You do not want to be embarrassed when someone mentions that they did not get an invitation card.
The best way to make a comprehensive guest list is to create one on cloud. You can access it anywhere, at any time. My mother had made a list of guests the traditional way- pen and paper while my brother and I created another one in our favourite 'MS excel'. We then added all of these lists and saved it on dropbox. There are many other options google drive, box etc. etc. I created one list for family and another for friends and shared the friends list with my fiancé to be able to ‘cross-invite’ each other’s friends.
It has been 3-4 months since I created the first draft of guest list and I still keep adding to it. Its easy as I don’t have to keep reminding myself to add the names when I get home, neither do I have to carry a wedding diary with me all the time. I just open the dropbox app and update my list!