You should begin shopping for publishers before you game is complete. This means that you should approach a few publishers with at least part of your game complete and working. Don't go to a game publisher with only an idea because they will probably turn you away. At least with some of your game complete you can give them a taste of what's to come. If you can't find a publisher to sell your game then it may be a good idea to release your game on shareware.
Shareware can be freely copied and distributed by anyone.
The common condition to shareware is that it can only be used freely for 30 days. The benefit of shareware is exposure. Because your game is freely copied and distributed, it may be seen by more people than if you decided to sell it. This was the most popular shareware game ever distributed. Your final option for distribution is the Internet.