GnuCash has some pretty nifty features for small business these days. Herman Oosthuysen has a good writeup, although it is a bit dated. I wouldn't follow it step-for-step since many of the details have changed and GnuCash has a good set of basic business accounts, and I'm not in Canada. But it's a good read.

One thing I had a hard time with was figuring out how to pay myself and how to account for things I bought for the business with personal funds. The magic word here is Equity. Paying yourself is debit equity, credit asset. Paying for a business expense out of a personal account is essentially a form of investing in your business, so it is debit expense, credit equity. I use GnuCash's Equity:Retained Earnings account for taking owner draws, and created an Equity:Owner Contributions account for investments.