Make sure that the bowl you use for mixing meringues is freshly washed and dried and preferable glass or metal. A miniscule amount of grease in the bowl can mean that your egg whites won't whip correctly. I normally store my eggs at room temperature, but if you put your eggs in the fridge for an hour or so before you are ready to bake, then they will be easier to separate. Separate each egg and add the whites to the whipping bowl one at a time. This makes it easier in case you come across a bad egg without wasting the rest. More importantly you can check the egg white. If you have the slightest bit of yolk in the white it can stop the egg whites from whipping. When the meringue has reached the right consistency handle it as little as possible with metal spoons or a spatula so that you don't allow the air to escape.