hiya nu gen!
To answer your question, you will need a properly drawn up contract of sale, your conveyancer/solicitor will furnish you with this. Don't scrimp by getting one from an agent and using this, the copyright on them makes them un-enforceable for non-registered agents, as I understand the legislation. (it shouldn't cost any more for the solicitor to give you one anyway!)
It's an interesting conundrum, selling privately. One thing always sticks in my mind... "You can't both save the same commission".
As a vendor, you are selling privately so that you don't have to pay a commission (I assume). But any purchaser seeing your ad will immediately think, hey, I can offer less, because there's no agent's commission to be paid.
For instance, If you want 250k in hand for your house, you will advertise it for 260k. You are thinking, hey, if I get 250, then it's all mine... But the purchaser is thinking, well, with an agent I would have offerred 250, but since there's no commission to be paid, I'll offer 245.
Also, it's the agent's job to get you the best price they can, so in all likelyhood, the agent will get your best price, even after their commission is taken out.
I guess it's obvious that I am biased in this respect, and I wish you luck with your sale, I hope it goes well.
Contact a local signwriter, they will be able to do a board for you, these are about $200. As Simon said, don't scrimp on the advertising, your ad should be about twice the average size of a single ad for a property in any of the real estate agent's lists, most people just don't see individual ads.
Hope it goes well!
asy