Hey,
Here some tips on how to clean your Gmail, which useful to avoid too much clutter and when your inbox shows full.
Search in Gmail for:
size:5MB = any email with an attachment over 5 MB. You could choose any number.
filename:mp3 = any email with an attachment of the mp3 type. You could search also wma, pps, avi, mpg, mp4.
Type is:unread = any unread email.
If you receive for instance many useless emails from Expedia, Yipit, Groupon, etc, just search for their name/email and delete.
Tip: If there are results that cover several pages, the following will show up, just on top of the results:
All 100 conversations on this page are selected. Select all conversations that match this search
Select the above to get rid of all in one shot.
You will need to empty the Gmail Trash to see the available space increase.