Usually when I want to search for a Facebook page or friend, I just look them up on the search feature. Facebook itself uses stuff that we searched on the site to push ads and related posts on our feeds.
Facebook allows users to check their activity on their account. This includes all the search activity on your account.
Access your search activity on Facebook
Login to your Facebook profile and click on the Activity Log button.
That will show you a list of all your Facebook activity. On the
right hand left hand side column you will see a drop-down to select Apps and Posts. From the list select “Search”.
Update: The image below is from an older Facebook design. The Posts and Apps shows up on the left-hand side now. You can simply visit the correct setting clicking on this link.
Now you can see all your search activity nearly categorized under its relevant date. You can delete search activity by clicking on the “Clear Searches” button or delete the queries one by one.
I guess by clearing the Facebook search history, I should expect Facebook not to use that data to serve me ads. I am not sure if Facebook does that or not but there is no harm in trying.
Facebook is definitely going to treat what people search for on its website with a lot more seriousness than before. It will surely be part of any monetization plan on their mobile platform in the future, so it might not be a bad idea to actually remove your search history on it.