An informative abstract is a brief comprehensive summary of the contents of a scientific article, legal document, report, etc.. A well written abstract allows readers to survey the contents of an article quickly by recounting the most important facts and conclusions of the article. Typically, an abstract appears on one of the very first pages of the report, often even on the title page.

An abstract is very important because:

1. it is read first.
2. it may be the only part of an article that is actually read (readers frequently decide on the basis of the abstract whether to read the entire article).
3. it is a means by which articles are classified and thus an important way of locating and retrieving an article.

Be concise and specific. Make each sentence maximally informative, especially the lead sentence. Be as brief as possible. Only abstracts of the longest and most complex papers require as many as 150 words. Be aware that many abstracts must conform to specific word limits (less than 150 words, less than 250 words), and make sure you are aware of any such limits for your abstract.

Be accurate. Only include information that appears in the body of the paper. Be sure that an abstract correctly states the purpose and content of the manuscript.

Define all abbreviations and acronyms. Spell out names of tests and drugs (use generic names for drugs). Define unique terms. Paraphrase rather than quote.

Be non-evaluative. Report rather than add to or comment on what is in the body of the paper.

Never use "I" statements. Report your information impersonally.

Detailed growth paths of embryonic frog and chick axons were measured as the axons elongated in dispersed cultures on acid-rinsed glass surfaces. Mathematical analyses demonstrated that under these conditions axons did not grow randomly but tended to grow straight. It appears that an axonal resistance to bending may be the cause of the intrinsic tendency for relatively straight axonal growth. The natural straightness of axonal growth may be an important developmental determinant of certain in vivo axon patterns.

Here is the same abstract presented in steps, with instructions for clarification (this example is from Elements of the Scientific Paper, by Michael Katz, Yale Univ. Press, 1985):

Detailed growth paths of embryonic frog and chick axons were measured as the axons elongated in dispersed cultures on acid-rinsed glass surfaces.
(State what was done. Use the past tense.)

Mathematical analyses demonstrated that under these conditions axons did not grow randomly but tended to grow straight.
(State the major result. Again use the past tense.)

It appears that an axonal resistance to bending may be the cause of the intrinsic tendency for relatively straight axonal growth.
(Present one major explanation. The present tense is a clue to readers that you are offering a general explanation.)

The natural straightness of axonal growth may be an important developmental determinant of certain in vivo axon patterns.
(Point out one significant implication. The present tense indicates a generalization.)