That's a question we as realtors often get from unrepresented sellers. To get the word out, you need to run newspaper ads. Have flyers made - make sure they are quality flyers. Send them to everyone you know, perhaps walk neighborhoods with flyers, put them up at work, day care, everywhere. You might even want to get a website. (Still with all these ways, your house isn't going to have the exposure it would with a realtor through the MLS.
And don't forget to get a quality sign made to put in front of your house - not one of those cheap red ones you can pick up at Lowe's or WalMart.
One last thing - you need to plan to spend some money to get the word out. You will probably want to plan on spending 1-2% of your asking price for marketing.
Hope that helps and good luck!