How to find out how much my house is worth?

Value of Property

1. How can I find out how much my house is worth? There are no comparable homes in my area.

This may be a bad sign for you, especially if you think your house is worth more than other houses in your neighbourhood. Homes maintain their value better if the neighbouring properties are fairly similar.
In your situation, you may actually have to talk to several Realtors, get their opinions, and come up with some sort of consensus. Without knowing why there are no comparable properties in your area it is difficult to give another suggestion. If your lot or home is over-improved for the area, that means the value will most not likely be what you think it is. If your home is much larger, you might not get the same cost per square foot as other homes in the area.
So I would talk to a bunch of Realtors and get their opinions. I would not recommend hiring an appraiser, however, even though a lot of books recommend this. Appraisers are better at "justifying" a price than in determining market value.

2. Where can I get information about the asking prices of properties that have sold during the last six months? I have found information on the selling prices, and would like to compare them to the asking prices.

The only place I can think of where you can obtain that information is the Multiple Listing Service (Realtor.ca). For that, you need to be a member, but you could ask an agent to obtain the information for you. I cannot think of any reason why an agent would not be willing to give you that information, so just ask one.
There really is not a concrete value in knowing the asking prices. There are different strategies in developing an asking price, plus a lot of properties start out over-priced to begin with. Comparing properly priced houses to over-priced houses, then lumping them together in some sort of analysis would skew your figures.
I can see how you could intend to use such knowledge for the purposes of negotiation, but with an informed listing agent, it should be a fairly ineffective strategy.
For example, recently I saw a web site where the agent was hawking his ability as a listing agent. He said the average home in his area sold for 93% of asking price, but his average listing sold for 97% of asking price. The implication was that he got more money for his sellers.
The truth is probably just that he priced his homes correctly to begin with.

3. How do you know whether the price of a home per square foot is reasonable or if you are about to make a bad decision?

Though this seems like an easy question, it is not as simple as it sounds.
Keep in mind that much more goes into the market value of a house than it’s square footage. For example, two houses next door to each other can have the same square footage, but if one has two bathrooms and the other has only one, guess which one will probably be worth more? It will also cost more per square foot.
However, if you compare recent sales of similar homes, the cost per square foot should be similar to those properties. You can ask your agent to provide you with comparable sales data.