You've unsubscribed to lists that you don't actually read and moved the others to an organized blog reader. Now it's time to clean up what's left.
As you go through the rest of your inbox, you'll need to quickly read through your emails and then make a fast decision about what to do with it. Don't over think this step. If you open an email that clearly will take more time, skip it and come back once you're done. The idea is to read through these as quickly as you can and then take an action step.
You probably have a ton of emails that are nothing more than a quick notification or filling you in on some information. Once you've read it, you're good to go. If you no longer need the email (for reference or otherwise) delete it. Just do it.
If you have an email that will take 1 minute or less to respond to, go ahead and shoot of a quick answer. No need to hold on to these. Respond appropriately and then delete.
Sometime I'll get emails with information that needs to be stored. For example, I save all the editor responses to my clients books. I'll reference these later when I pitch their next project to see if they might be interest. The trick here is to make sure you have clearly labeled folders to store this information, otherwise it crowds up your inbox and is impossible to find.
Mark as to-do
You probably have a to do list whether it's a physical list, a note on your phone or a mash of postit notes. If you have an email that gives you an action item, add it to your list no matter what kind of list it is. Once you've got the item on your list, delete the email. You can also organize these in a to-do folder within your email, just make sure to check it regularly.
If you've completed these steps then the only emails you have left in your box are those that are longer or more complicated. Ideally, you won't have too many of these, but if you do, make sure to set aside enough time to go through these.
I try to keep my inbox low enough that I don't have to scroll to see the full contents. This doesn't always happen (honest moment: it happens a lot less frequently than I'd like), but when my inbox is clean I feel that I'm able to focus more on the work I have to do.