I've been using a few methods to find retail discounts over the years.
To start, remember the good old flyers? These paper ads may seem dated in this digital age, but they remain a valuable source of information about sales and discounts. Most big retailers still distribute weekly flyers with product deals that can help you save significantly. And if you don't want the paper, you can find those flyers online too, just check this Giant Tiger weekly flyer for example.
Signing up for a retailer's loyalty program is also a great way to receive exclusive discounts and promotions. Most large stores have such programs that reward regular customers with points, coupons, or cash back on purchases. You might also get special discounts on your birthday or membership anniversary.
Many big retailers also have mobile apps where they push exclusive deals and give users early access to sales. These apps may also allow you to scan items in-store to see if there are any available discounts or cheaper alternatives. Using one of these is a great way to save money.