If you're worried about over-sharing your personal data, you're not alone. Companies, increasingly fewer, bigger companies, have more of our private information than ever, and not just that: they're also much more capable at using it.

It can be a tough call between trusting a giant company whose main goal is ad sales, and denying yourself the use of many really useful services and opportunities to connect or communicate.

But what exactly are you handing over when you sign up for those terms of service, and what can companies do with it? And, if you don't like it, what can you do besides 'delete account'? Here are a few suggestions:

1. Form a pretty good picture of who you are, from your Facebook and Twitter posts and likes.

The University of Cambridge Psychometrics Centre came up with this tool, which pulls your likes and posts from Facebook and/or Twitter (you have to log into your account) and spits out a load of best guesses about who you are, and how you compare with others, including your "big five" personality traits.

You can also not connect a social media account, and just input something like 200 words of text and see what the machine thinks of you.

2. Manage your Google data

Google has a lot of data on you, but it’s there for you to download or delete if you wish.

You can find your search history, and you can see whatever Google knows about your habits. You can delete it if you like - or stop saving it in future. Google say if you delete it, it’s permanently gone. For instructions on how to stop keeping data, see here

You can also download zipped files of your history from many Google apps. Maybe you can’t think of what you would do with a massive spreadsheet of every YouTube video you’ve ever watched, or maybe you can see something wonderful about revisiting streams of music you loved five years ago. It’s there, anyway, for your electronic navel-gazing. If you don’t like your searches being kept, incognito mode is your friend.

You can delete or stop capturing certain data

3. See what you’ve shared publicly on Facebook, that you might have forgotten about.

Stalkscan takes anyone’s profile - no, you don’t need to log in, and nobody needs your password to look at yours either - and collects all the information that’s available to the public. Every pub you’ve checked into, every event you said you’d attend, every photo that’s visible to anyone. If you think you gave your profile enough of a once over before adding your boss on Facebook, this might be a wake up call.

4. For the really curious: watch how Facebook tracks your activity on the site.

The Data Selfie Chrome extension lets you track your Facebook activity over time (the way Facebook would track you), such as time spent on other people’s profiles, likes, and various other things you might not even notice you’re doing, and you may turn out to be more of a creep than you thought you were. If you share a computer and leave yourself logged in on Chrome, be warned, you probably don’t want your loved one(s) seeing how long you spent looking through your old classmate’s photos. Frankly, you probably didn’t want to see that either. Shudder.

Facebook app list
Apps left after a major cull

5. Remove permissions from those Facebook apps you forgot about

In the menu on Facebook's site or app, go to settings. From there, you have plenty of options for privacy and so on. Probably, if you select 'Apps' you'll see a ton of apps you either installed and used once - or don't remember installing at all. Everything that pops up with a little request to know your name, age, etc, or post to your account, will be here, and you can remove those permissions if you don't want them any more. 

That quiz on which Game of Thrones character you are that you took years ago probably doesn't still need to know what you're up to on Facebook.

Also: Next time something asks for permission, you can usually disable most of those extra things and just allow the app to know your basic information - name and age, etc.