If you add a beaten egg slowly to your batter mix it prevents the batter from becoming too stiff.
Always use eggs at room temperature when baking with them.
If you want firm meringues, add a teaspoon of cornflour to the sugar before beating into the egg white, and to make meringue with the same number of eggs, add one tablespoon of water per egg.
Eggs will stay fresher longer if you store them pointed end down.
If you forgot to get your eggs out for baking then just pop them into a bowl and cover with hot water. Take them out after a couple of minutes and use for baking as normal.