If I talk specific about Adwords here, look for the keywords which have high bounce rate history and are not worth for you in the sense that you have not received any conversions out of them and they have been costlier for you. You can simply pause them and try their variations.
Another way could be to work on your keyword match types. Chances are that you are using Broad match keywords in majority. Look at the search terms and eliminate the irrelevant ones by adding them as negative keywords. This would lead to more relevant traffic and might assist in lowering bounce rate for Adwords campaigns.
I could also relate high bounce rate of your Adwords campaigns to the destination URL or landing page you are using.
Make sure that your keyword, ad copy and landing page are in relation to each other. Make sure that what you are advertising in your ad, you are taking users to as specific page as you can in your website.
You might consider working on your website with High Bounce Rate pages. Read this article for more insights.
Hope that helps!
Re: bounce rate