This writeup applies specifically to the Forgotten Realms and Toril. YMMV.
High Elves are slightly taller than average humans, standing at 5 1/2 to 6 1/2 feet tall, although they are much more slightly built, only 90-120 lbs for an average male High Elf, with females being even lighter than this. High Elves have a very pale complexion, despite their love for the sunlight. They do not appear to tan. Most High Elves possess blond hair and blue eyes, although there is a slight variant of the race which has sandy brown hair and green eyes. High Elves prefer pastel-coloured clothing, although many use forest green or camouflage cloaks for hunting in the forests. Their features are elegant and finely-chiseled, with high cheekbones and slanted, piercing eyes. Other races find their faces to be exotic and alluring, and this coupled with their natural grace makes them very charismatic. They also, of course, have the classic pointy ears particular to the elven race.
One of the noted features of High Elves is that their hands and fingers are half-again as long as a human's. This may help contribute to their excellent dexterity. While High Elves are more slight than humans, they have a very wiry musculature that can contain much more power than their form would suggest. They do tend to be more frail, however. High Elves have much more precise eyesight than humans, as the slant of their eyes gives them a wider field of vision, as well as the ability to see greater distances. They possess a peculiar sort of infravision, which operates on the basis of heat and life force. High Elves also have excellent hearing, as the increased size of their ears allows for a more efficient collection of sound waves. This coupled with their extremely efficient sensory processing allows High Elves to detect sounds far too faint for humans to percieve.
High Elves do not sleep. Rather, they enter a meditative trance state called a "Reverie", which refreshes them just as sleep would for a human.
High Elves do not age in the same manner as humans. They may live to be up to 700 years old, and do not show visible signs of aging in their later years.
Attitudes and Personality
High Elves consider their race to be superior to all others, including other subraces of Elves. They feel that they are the elven subrace which has maintained the "pure" essence of Elfdom. High Elves have a reputation for being particularly haughty and arrogant, but mainly they are just distrustful of other races. One of the best ways to be a friend with a High Elf is to have a parent or grandparent that the elf trusted.
High Elves, like other elven races, refer to themselves as "Tel'Quessir", which roughly translates as "The People". Non-elves are referred to as "N'Tel'Quessir", which translates as "Not-People". This is not nearly as racist in practice as it first appears, but merely shows the bond that elves feel with members of their own race. The only race that the High Elves truly despise are Orcs.
High Elves treat "not-people" with respect and politeness, although they may come across as condescending and paternal. They do not tend to forge friendships with the shorter-lived races, but considering the pain involved in watching your friends grow old and die over the years, this is understandable.
High Elves prefer the freedom of the individual over the good of society, and their rulers are respected and obeyed by choice. These rulers invariably choose not to practice their power unless the need is great.
This race lives in harmony with nature, never taking more than the land can give, and always taking care to give back more than they take. Their homes tend to be built into trees or mountainsides, and the architecture is designed to blend into nature rather than take control of it. They always strive to protect nature, and make sure that it always remains in the world.
High Elves tend to take life at a leisurely pace, which is understandable considering their lifespan. They have a great love for finer things such as art, music, and dance. They love to spend their days basking in nature, and to spend their nights dancing under the moon. High Elves do indeed tend to lead fine lives of freedom, nature, and the sheer joy of being alive.
High Elves have a particular affinity for magic, considering it a living force to be experienced rather than a tool or weapon to be wielded. High Elf mages are some of the most powerful in the Realms.
Even though High Elves have a natural love for life, their ability to deal death is highly refined. In battle, they tend to prefer the bow, although they are also highly skilled using the longsword and shortsword. Watching a High Elf in battle with a sword is much like watching a brutal and deadly, yet hauntingly beautiful dance. Their bows also have an ingenious design scheme which includes metal inlays along the sides. This allows a surprised elven archer to parry blows with the bow while drawing a more appropriate weapon.
In group battles, High Elves often make use of snipers, camouflage, and skirmish tactics to decimate enemy forces while maintaining minimal loss of elven life.
Most elven adventurers encountered in Toril are High Elves.
On a more personal note, I once played a High Elf Weapons Master who could only enter his fighting trance if he was under the influence of the particularly high quality pipeweed of The Shire.
He was, in every sense of the phrase, a "High Elf".
His love for the halfling leaf, however, did not dull his wits in the *SLIGHTEST*.