The Sagittarius symbol (also called Sagittarius glyph) is a shorthand representation of the Sagittarius archer (see below). However, as with the archer itself, much is based both in interpretation and the preference of the writer, and can range from simple to extravagant.
The astrological symbol for Sagittarius represents the bow and arrow. Above are some examples of commonly used styles for the Sagittarius symbol. Each of these is equally valid - there is no 'correct' version as long as the general shape is maintained. It does make more sense intuitively to keep the bow line at a right angle to the arrow, but that may be getting a little picky.
Origins of the zodiac symbols and signs
The word 'Zodiac' means circle of animals (though note a couple of signs aren't animals in the normal sense). These 'animals' were based originally on the pattern of the stars in their corresponding star constellation. Basically what the earliest astronomers and astrologers saw when they squinted at the night sky.
Due to this although Sagittarius will always be represented by an archer (whether man or centaur), there isn't any one 'correct' shape or design for that archer (or centaur). It's a cosmic game of join the dots, and some constellations even have alternative ways to form the animal from the dots (stars).
Sagittarius the archer (or centaur)
Any picture of the shape, concept or profile of an archer (or centaur) can therefore be comfortably used here. Designs range from the space-age to the ancient, and are limited only by the imagination of the artist, as long as it gets the point across.
Below is a representation of Sagittarius the archer (and the Sagittarius symbol, inset) from a medieval wood carving from the 16th century. While it's not suggested this is a great picture (hey, you try carving something into the side of a tree which will look sexy in 400 years time!) it does show how the basic concept of Sagittarius hasn't changed much over the centuries.
We have a separate article on Sagittarius tattoos