You have been fairly general in your post...so the answer will also have to be general.
Meta tag information in the recent versions in in /includes/language/english/meta_tags.php
In your admin > tools > developers toolkit > you can search for text strings. i.e. the information box has a 'contact us' listing... search for that and the instances will be displayed with the files path & name. Open the file using your editor and adjust as desired. If you want to remove a listing, remove the text between the single quotes, just insure that you leave the single quotes. save and transfer to your override folder.
Most of the descriptions that are in the information sideboxes are in the /includes/languages/english.php file.