As a reader I don’t always care what colour the protagonists’ eyes are or how tall or short they may be. What I care about is whether or not he’s a brute or a sensitive man. Whether he is a willing hero or was thrust into the role. If you can show this through his physicality, great. If you can juxtapose his personality with how they look, even better. (Perhaps your protagonist is tall and muscular but so cowardly he will never succeed as a soldier) What you want to avoid is a running list of what they look like. This can be very boring.
In Raymond E. Feists’ Magician: Apprentice, he subtly slips in two small descriptors.
Pug danced along the edge of the rocks, his feet finding scant purchase as he made his way among the tide pools. His dark eyes darted about as he peered into teach pool under the cliff face, seeking the spiny creatures driven into the shallows by the recently passed storm. His boyish muscles bunched under his light shirt as he shifted the sack of sandcrawlers, rockclaws, and crabs plucked from this water garden.
We know his eyes are dark. We know he’s young. That’s it, and it’s enough.
The use of metaphors and similes is not a bad way to spice up your description. In Philip Pullman’s The Golden Compass he describes Lord Asriel in the following way,
Lord Asriel was a tall man with powerful shoulders, a fierce dark face, and eyes that seemed to flash and glitter with savage laughter. It was a face to be dominated by, or to fight: never a face to patronize or pity. All of his movements were large and perfectly balanced, like those of a wild animal, and when he appeared in a room like this, he seemed a wild animal held in a cage too small for it.
The great thing about this character description is it evokes emotion in the reader. We’re intrigued by this character and maybe even a little scared.
Before describing your characters ask yourself, does it enhance the readers experience to know what they look like? Are there physical features important to their character? Why? Can you evoke emotion with the description?
Don’t forget, you can always have your reader decide what they look like by not describing them at all. It’s your choice.