It is said that the God Apollo was very handsome and strong. He was ever youthful and always had rich wavy golden hair, to match his name as the God of Light.
All images of the God match this description, for example:
These are obviously all just artists impressions of the God, as what a God looks like is down to the believers own impersonation. However usually people have some guidance about a God's appearance from stories told about the God.
In this case, Apollo was the God of Light, so instantly one would think of golden, light hair, and so this is how he was depicted in images from mythology.
He was almost always portrayed with a bow and arrow, as this was the weapon that he would use in many mythological battles. He would also often be carrying a lyre, which is a type of musical instrument, to show his love for music.