Remember that the announcement is not a retelling of the text. It is therefore essential to exclude the citation of the original without quoting. You should also not use the expression "I think", "I believe", because the tastes of any person is subjective.
What you like may not be interesting to other people. Therefore, the announcement must clearly display the essence of the article without your opinion about it. But you can use the reviews from sources that are familiar with your article and enjoyed some popularity.
Your announcement should be clear to any reader, so if it will be filled with scientific terms and complicated turns of phrase, its popularity will considerably decrease, which is not desirable for quality articles. Try to avoid cliches and well-known facts.
Not very welcome presence information that do not belong to an annotated article, as well as redundant information. You have to stick to artistic, scientific or neutral style (if this has article).
The size of the announcement should be for the volume of 150-500 characters with spaces.
In any case, do not use words or sentences in uppercase, that is, when the Caps Lock button. Such texts are hard to read, they only irritate Internet users.
Write the announcement correctly. Do not rely on that wrong written announcement "will ride". If you began writing the annotation, then do it well. In a pinch you can turn to knowledgeable people or check a word in MS Word.
If you use a picture, be sure to attach it. Colorful images always attract readers and make them click the link to read the article, even if the announcement is not too interesting.