You can use the search bar at the top of the Gmail page to filter for unread messages, or messages with a variety of attributes.
- displays all messages in your account that are unread
- is:unread in:inbox
- filters your inbox to display only unread messages
- is:unread in:inbox label:important
- filters your inbox to display only unread messages that are labeled "important"
- is:unread from:sally
- displays all unread messages from anyone named "sally"
"is", "in", "label" and "from" are just a few of the many operators you can use in the search bar to filter and find messages. For more information and examples, see Search operators you can use with Gmail.
Inbox Layout - Unread First
You can also set your Inbox so that unread messages always appear on top. To do this click on the down caret next to Inbox and select "Unread first". For more information on customizing your Inbox view check out the Change your Gmail inbox layout page.