Make use of the Gmail Inbox category system - You can segment your incoming emails into different categories. There are 5 to choose from: INBOX, PROMOTIONS, FORUMS, UPDATES, and SOCIAL. This saves every single email arriving in your main INBOX and keeps it from getting overcrowded. You can create rules in your settings.
Use labels to create specific folders - Creating folders for specific incoming messages or client emails/specific correspondence means you can keep your messages tidy and know where to find or allocate them. This clears up your main inbox of clutter. Another great feature if you like it visually appealing, is you can colour-code each label.
Filter your incoming email messages - If you use multiple email addresses within Gmail, setting up a filter to send each email to a specific folder clears out your main inbox of all the clutter. You can also filter specific emails you receive from clients/enquiries etc to go straight into a specific folder.
Set up email response templates - Creating and saving a template for standard responses is a great way to save time typing up an email you respond to on a regular basis. They can be created and named and saved for your most common responses.
Use the Gmail mark as unread option - Marking an email as UNREAD (mostly after you have actually read it), means you aren't missing out on actioning it. An UNREAD email can be seen as the one you haven't handled yet and it eliminates the potential to let it fall by the wayside.
If you need help managing your Gmail inbox, drop me a message - I'm here to help!