An Abstract is an important element of any technical report or any research paper/article. It is something which people normally prefer to read before taking a look at the whole article. The abstract must contain the enough information which highlights and give the complete essence of the article.
Normally abstract should deliver objectives of the research, methods that one has used for research, key results obtained and a clear and concise conclusion.
The abstract should contain minimum 100 to 200 words. The content of the abstract should be clear and concise.
It should highlight the main objectives and motivation of the research. Do not write an equation and related stuff in it.
Avoid putting references in an abstract. One should not use in this 'paper' or 'article' but use 'research' or 'investigation'.
The abstract must have enough information which develops the interest to read the full paper or article.