What steps should I take to lawfully visit the United States as a tourist immediately after visiting on a B-1 visa?

As a Canadian, you do not need a visa to be admitted in B-1 (business visitor) or B-2 (pleasure visitor) status.

(You are also not eligible to participate in the Visa Waiver Program; Canadians are exempted from the visa requirement by a different section of the law. If you try to apply for ESTA, you will see that "Canada" is not available in the list of countries. Among other things, this means that your period of admission will normally be the 6-month period for regular B-category visitors rather than the 90 days given to VWP visitors.)

When you travel to the US for business, be sure to say this to the immigration officer so you are admitted in B-1 status rather than B-2 status. In practice, nothing is likely to happen if you're admitted in B-2 status, but technically you're not supposed to be engaging in business activities as a B-2 visitor.

The US allows people to change their nonimmigrant status without leaving the country. So, in theory, you could file an application with USCIS after your business activities are done so you can remain in the US as a tourist. However, the USCIS page on the procedure says that you don't have to do that:

You do not need to apply to change your nonimmigrant status if you were admitted into the United States for business reasons (B-1 visa category ) and you wish to remain in the United States for pleasure before your authorized stay expires.

Canadians don't need a visa or ESTA to visit the United States for less than 180 days. Everything permitted by B-1 is permitted without one and very few special cases need a B-2 visa but being a tourist for a short period is not one.