The French used to have a wonderfully simple, elegant way of determining whether the egg whites have been properly beaten. You flip the bowl over your head - you'll quickly realize if more whisking is needed. Of course, this is before mixers and other electronics were commonplace. But until I get my dream kitchen, forearm strength will have to suffice.
Slowly add caster sugar, making sure to maintain volume. A handkerchief tied around the forehead keeps sweat off the brow from dripping.