Ensure you are logged into your Google profile, then navigate to: https://adssettings.google.com/.
At the top of the page, you can determine whether or not you’d like for Google to personalize your advertisements based on your perceived interests.
In the ‘How Your Ads are Personalized’ section, Google lists the assumptions they have made about you based your activity in your Google account, data from Google’s partners, and Google’s “estimation of your interests.”
If you click into each interest, you can toggle it on and off and, sometimes, you can adjust the information they have.
Towards the bottom of the page, there is an opportunity to turn off ads about topics such as alcohol and gambling in the Ad Categories on YouTube section.
Notice they include categories such as gender, income, education level, age, etc.
Facebook:
Log in.
Click on the down arrow on the top right of the site and select Settings and Privacy -> Privacy Shortcuts.
Select Ad preferences in the left navigation pane or simply scroll down to Ad preferences on the right pane.
Select Review your ad preferences.
Select Advertisers, which shows the advertisers you have recently seen or will see, gives you the opportunity to remove those advertisers so you no longer see their ads, shows you which advertisers you’ve hidden, and shows you who’s ads you’ve interacted with.
In the left navigation pane, select Ad Topics. Here, you can opt out of seeing ads that fall under categories like parenting, alcohol, pets, and politics.
In the left navigation pane, select Ad Settings. Here, you can opt out of personalized ads based on activity outside of Facebook, see which topics are used to determine which ads you see, see which advertisers have purchased your data, restrict Facebook advertisers from following you to other websites, and determine who can see your social interactions.
Twitter:
Log in.
On the left side navigation pane, select more and then select Settings and Privacy.
In the middle Settings pane, select Privacy and Safety.
In the right side Privacy and safety pain, select Ad Preferences under Data-sharing and off-Twitter activity.
From here, you can opt out of personalized ads, see your Twitter interests based on your profile, activity, and topics you follow, and view which advertisers have purchased your data in your advertiser list.
In ad interests, notice that these categories aren’t necessarily things you’ve liked or followed -- they are assumed interests based on your activity within the app. If you follow Joseph Gordon-Levitt, for example, Twitter might assume you also have an interest in 3rd Rock from the Sun, Seth Rogan, and Hit Record.
Instagram:
Log in.
Click on your profile picture on the top right of the site and select settings.
In the left navigation pane, select Privacy and Security.
In the right Account Privacy pane, scroll down and select Account Data -> View Account Data.
Scroll to the bottom of the screen to Ads -> Ad Interests -> View All.