Several problems seem to occur over and over, and I have prepared a little list of things to look out for. While the items below might not all be considered errors, I believe paying attention to them will improve the clarity of astronomical papers. This is a form letter, and many of the items may not apply to your manuscript. I welcome suggestions for modifications or extensions of these guidelines. 1. Astronomical nomenclature has been a continuing problem. For Journal publication, all objects mentioned must be unambiguously identified. The "lifetime" of a Journal article can be decades, and nicknames that are popular today may fall out of use in the future. Newly-discovered objects must be assigned proper names for future reference. The specific requirements for Journal articles are: a) All objects must be labeled by a "Class I" or "Class II" name. (See information at http://cfa-www.harvard.edu/~willner/desig.html ). Punctuation (e.g., space, equal sign, slash, dash or minus sign, parentheses, and colon) within and between names must be used correctly. b) Pre-existing source names should not be changed, but if they are non-standard or unfamiliar, a reference to the original source of the designation should be given. New names may be assigned to previously-known sources, e.g., for consistency or clarity or as part of a compilation of data. If new names are created, cross-reference to old names should be given. c) Newly identified objects should be assigned Class I names, and the exact form of these names must be made clear for future use. d) All new names assigned (per b or c above) should follow IAU guidelines. For a few objects, incorrect names have been used in the literature more often than the correct names. Authors should consult with me about individual cases, but very often the solution will be a footnote giving both the correct and incorrect names. References to the guidelines and additional advice is available at http://cfa-www.harvard.edu/~willner/desig.html I strongly encourage authors who have questions about designations to read that material. 2. Figures together with their captions should be as self-contained as possible. The caption (or the figure itself) should describe the symbols used, all lines and curves, and anything else directly related to the figure. The concept applies more weakly to tables, where it may be necessary to explain in the text how tabulated quantities were derived. Even for tables, though, careful use of column headings and table notes can often simplify and thereby clarify the manuscript. In most cases, at least the basic nature of each column should be apparent without reference to the text. Information given in figure captions or table notes should not be repeated in the text. There is no need to enumerate table columns, explain which symbols show what, or to describe what readers can plainly see for themselves. The text should explain the scientific implications of the figure or table. 3. The pronoun 'we' is no longer forbidden in scientific manuscripts, but it can be distracting if used excessively. A good rule is to use 'we' only where there is an element of personal judgment or where the syntax would otherwise be horribly convoluted. Changing sentences to passive voice is one possibility, but a much better solution is to rewrite the sentence with an added idea. For example, instead of "We fit a blackbody to the data," write "A blackbody is a good fit to the data," or even better, "A blackbody fits the data to within 10%." The improved form adds the idea that the fit was a good one, and the final form makes the result quantitative. Both improved forms make the object of the "we-sentence" the subject of the new sentence. Quite often a relevant idea to add can come from the very next sentence in the manuscript. 4. Instead of "In Figure XX we show...," a much simpler construction is "Figure XX shows...." The same applies where the noun is Section, Table, or even the entire paper ("This paper presents...") and for any verb. 5. Data are given "by (authors)," not "in (authors)." The authors are people, and the latter evokes an unsavory image. 6. Please be careful about using 'order' versus 'degree'. 'Order' is a general indication of complexity; it is proper to refer to the "order" of a differential equation or, for example, "accurate to first order." 'Degree' always denotes a polynomial and is almost always better when it applies because it specifies the functional form exactly. You can often simplify your text by referring to a second degree polynomial as a quadratic and a third degree polynomial as a cubic. 7. Prefatory phrases such as 'Note that...', 'It is important to note that...', 'It can be seen that...', 'It is clear that...', 'We find that...', 'We see that...', and many others are usually best omitted. In general, they tend to detract from rather than emphasize the importance of what follows. If you want to emphasize, usually the best thing is to use a stronger verb. Even adverbs like "very" can have a dubious effect. (Cf. "...can have a _very_ dubious effect.) See also item 3 for phrases involving 'we'. 8. Please don't use 'error' where you mean 'uncertainty' (or vice versa, for that matter). Even though the word is often used loosely, 'error' is a synonym for 'mistake'. A statistical estimate of some true value has an 'uncertainty'. ('Error bar' is acceptable; it is one of the many anomalies of English usage.) 9. Explanation of color figures can be confusing. As guidelines, "true color" means an image as it would be seen by human eyes. "False color" once meant an image as it would be seen if our eyes were sensitive to different wavelengths than they are (e.g., an infrared JHK image), but the term has been so badly misused as to have lost all meaning. Probably "composite color" is the best phrase for such images, but the caption must explain what each color represents. If color is used to indicate surface brightness -- a practice that is seldom justified, given that a grey-scale image can usually show the same information -- the result is a "coded intensity" image. I'm not sure there is a good term for images where color represents some unrelated quantity such as radial velocity; again the caption must explain. (I welcome suggestions.) 10. All displayed equations should be numbered, even if the text does not refer to them. Other papers that refer to yours may need to cite specific equations. 11. Figures and Tables should be numbered in the order in which the text refers to them. 12. Dates should be presented in the order year-month-day. Please use a four-digit year number. The ISO standard (for tabular dates) is to put a hyphen between year and month and between month and day, but I don't insist on that. 13. The abstract should state the principal methods employed and summarize the main results of the study. The abstract should be written for non-specialists and should be as concise as possible consistent with clarity. In particular, it should avoid detailed explanations and qualifications. Where results may be subject to doubt, that can be indicated by choice of verb (e.g., 'suggest') or adverb (e.g., 'likely'). It is not necessary to list all of your minor results if a specialist will expect their existence from the rest of the abstract. The abstract is not the place to summarize previous results except on the rare occasions when a brief summary of an unfamiliar problem needs to be given. Nor is it the place to explain the motivation for your work nor to "advertise" how new and wonderful your work is. Mention of possible future work also does not belong in the abstract. The abstract should not contain symbols except for the most familiar ones. ('M' for mass is OK, but anything less familiar than that is dubious.) Key results should be explained in words. 14. Use proper verb tense. Work was done in the past, but results are (we hope!) still true in the present. 15. Be careful to use words with the intended meaning. Some uses that are common in casual speech are not precise enough for a formal scientific paper. One common example is item 8 above; others include: "Thus" means "in that way;" "therefore" means "for that reason." "Hence" means "from here," not "therefore." "Since" denotes time order; "because" denotes causality. "Optical" denotes a set of techniques, "visible" a range of wavelengths. 16. Make sure each paragraph starts with a self-contained and descriptive topic sentence. A topic sentence containing "this" or any pronoun without an obvious and immediate antecedent is usually a bad idea and is a "red flag" to have a closer look. A good exercise is to read only the topic sentences and verify that the ms makes sense when read that way. 17. Specify physical quantities precisely. For example, "flux density" is per unit frequency or wavelength (e.g., Jy); "flux" is flux density integrated over a bandwidth (e.g., W m^-2).