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When you have an item selected and press "a" on the keyboard, the pop-up to assign the item appears. This is usually faster than navigating to the field for Assignee.
When you have an item selected and press "." on the keyboard, the 'more' menu pops-up, allowing you to quickly change (for example) the item status.
At the top of a team board you usually find Quick Filters. These are specifically designed for your team board.
By clicking one of these Quick Filters, you narrow the board filter, hiding some or many items to fit the Quick Filter criterion. Deactivate it by clicking it a second time.
It's possible to select multiple Quick Filters, narrowing your selection of items on the board further and further.
Your team board admin can maintain Quick Filters for you: change them, or add new ones.
How can you find out who your team board admin is?
Go to Board (right hand side) > Configure.
Under General (left hand menu) > Administrators you can find the name(s) of your Team Board administrator(s). They are your first point of contact if you want anything changed on your Team Board.