In Ontario, your contract, the actual Agreement of Purchase and Sale, is very likely an Ontario Real Estate Association standard form contract. This standard form of contract will typically be modified to include the particular conditions that you and your agent have negotiated, but the bulk of this document is pre-formulated. Before you sign an agreement, you read it, and if you have any questions, you should ask your agent to explain what the clauses mean.
I would recommend that you have your lawyer review the agreement before you sign it. It can be very difficult to extract yourself from an agreement once it has been signed, so it is important that you can actually perform what is expected of you in the contract - you will not know what those things are unless you are familiar with your agreement.
As an example, one little thing that I have noticed is that contracts will typically state that the time for the closing of the transaction is 6:00 p.m. on the date of closing. Unfortunately, the electronic registration system will only allow registrations until 5:00 p.m. This may seem silly, but it could cause problems. What this indicates to me is that the people who are giving these documents to home buyers and sellers are not explaining what they really mean, or that they are just not paying attention.
As a home buyer, if you are reluctant to have your lawyer review your agreement before you sign it, you may at least want to consider adding a condition that makes the deal subject to the approval of your solicitor within a certain amount of time of accepting the offer.