Price comparison tools can be a smart way to ensure you are getting the product you want at the best possible price. Here's how you can use them effectively:

**1. Identify the Product**: The first step is to decide what item you want to buy. It could be anything from a book to a pair of shoes or a new refrigerator. 

**2. Find a Price Comparison Tool**: There are several price comparison websites and apps available such as Google Shopping, Price Grabber, Shopzilla or apps like BuyVia, ScanLife, and Mycartsavings. There are even browser extensions such as Honey and InvisibleHand.

**3. Search the Product**: Once you have identified a tool, input the product you’re looking for into the search bar. Some apps will let you simply scan the barcode of the product. 

**4. Assess the Results**: The tool will then provide a list of retailers selling the product along with their prices. Review this information carefully. Some tools also provide customer reviews and shipping costs or might direct you to second-hand prices on eBay.

**5. Look for Offers and Coupons**: Some tools help identify any coupons or discounts you can apply to get even lower prices. 

**6. Check Out Securely**: Once you’ve chosen the lowest price, click the link which will take you directly to the retailer's site. Any reputable price comparison tool will only link to trusted retailers, ensuring safe transactions.

**7. Monitor Prices**: Some tools allow you to track price drops for specific products, alerting you when the price decreases.

**8. Local Comparisons**: Some apps have features that let you check whether an item is cheaper online or at a nearby local store. BuyVia and ShopSavvy are examples of such apps.

**9. Compare Services**: Websites like Compare.com allow you to compare pricing not just for items, but also for services like insurance, mobile plans, etc.

**10. Factor in Shipping and Handling**: While an item may be cheaper on one site, high shipping costs could tip the balance. Always consider the all-in cost, not just the list price.

Using these comparison tools makes it easier to find the best deals, helping save money in the long run. However, remember to check the credibility of the online retailer before proceeding with the purchase.

Absolutely, here are some reliable price comparison websites and apps that you might find useful:

**1. Google Shopping**: This is a robust tool where you can input any product, and it will compare prices across numerous online retailers. You can even sort by price, review score, and other criteria.

**2. PriceGrabber**: This website allows you to compare prices on a wide variety of items from different online and local retailers. It also includes product reviews and allows users to set up price alerts.

**3. Shopzilla**: Similar to PriceGrabber, Shopzilla compares prices for products across categories and highlights the cheapest and most expensive options. It includes customer reviews and also lists alternative products.

**4. CamelCamelCamel**: This website is specifically for Amazon price comparisons. It tracks millions of products and alerts you when prices drop.

**5. Honey**: This is a browser extension that compares prices and additionally applies any available coupon codes to your order during checkout.

**6. InvisibleHand**: This is another browser extension that notifies you if the product you’re shopping for is available cheaper from another retailer, including estimated shipping costs in the comparison.

**7. BuyVia**: This mobile app provides price comparisons from thousands of online and local retailers. It includes reviews and gives you the ability to set up alerts for price drops.

**8. ScanLife**: This app lets you scan a product's barcode and compare prices from online and local retailers.

Remember, while comparing prices, also consider factors like shipping costs, delivery time, and the reputation of the online store. You want to ensure you're not just getting the best price, but also reliable service and easy return policies.