If targeted advertising troubles you, here are some useful tools:
Opt out of targeted ads
The Digital Advertising Alliance Of Canada allows you to opt-out of targeted ("online behavioural") advertising from 117 companies.
Limit ad tracking on your mobile device
iOS, Android, and Windows Phone all have options for this. Here's how you can prevent ad tracking from happening on your phone.
Enable Do Not Track in your web browser
You can configure your web browser to send a "Do Not Track" signal to the websites you visit. Note that while some websites obey this signal, not all do.
Use privacy-enhancing browser plugins
Several browser plugins, add-ons, and extensions can help you block invisible tracking code on web pages. Ghostery, Disconnect, and Privacy Badger are popular free choices, and there's a good list at alternativeTo.