Conventions for formatting lists are simple and straightforward, but many writers (and their editors) seem not to have gotten the memo. Here's an outline about how to outline:
1. Numbered and Unnumbered
Two basic categories for lists exist: numbered and unnumbered. Many numbered lists that people use online and in print have no need for numbers, because numeration implies a prioritized sequence, such as one of chronology. Number your lists only if there's a rationale for ordering the items exactly as they're listed.
2. The Bullets
The items in unnumbered lists are often preceded by dots or other symbols known collectively as bullets, though such markers are technically not necessary, especially in a recipe or a materials list. (In those cases, it's implicit that the ingredients or components are added or constructed in the order listed — it's actually a numbered list that needs no numbers.)
3. The Introductory Sentence
When you set a numbered or unnumbered list up with an introductory sentence, it can be a complete sentence or an incomplete one, depending on how the list items are constructed. But follow it with a colon only if it's a complete sentence. For example, you can write "To ensure success, consider these tips:" Alternatively, you can write, "To, ensure success, make certain that you" — but only if each item in the list can independently complete a sentence starting with that setup.
4. The Single Items
If the setup is a complete sentence, each list item can be a single word, a phrase, or a complete sentence, but it's best if you're consistent within a list. In this case, capitalize, and use a period, only in complete sentences. (And don't deviate in how you form words, such as whether verbs appear in their root form or with -ed or -ing endings, for example.)
5. Punctuation
If the setup is incomplete, only phrases that complete the setup are appropriate, and each one should end with a period. Don't use commas or semicolons, and don't append and to the second-to-last item.
6. List Or Not?
Before formatting a list, make sure it's best displayed as such. A group of just a few items might better be run in, meaning simply included in a sentence. (Commas are sufficient to set off the items in a simple list; use semicolons only if list items themselves contain commas.)
Conversely, lists consisting of items more than one sentence long are cumbersome, and these elements are usually more effectively presented within paragraphs or as separate paragraphs. In the latter case, they can be numbered, if necessary, or perhaps equipped with a heading for each item, if the items are more than a couple of sentences long.
7. Separators
Also, in run-in lists, avoid separators like "1)" or "(a)" unless the wording or the punctuation fail to distinguish the items; even then, consider whether revision or reorganization can improve the clarity of the list.
For simple outlines that have a couple of levels, use, in turn, roman numerals and lowercase letters. When constructing complex outlines, however, follow this standard sequence to identify items in each level:
roman numeral
uppercase letter
arabic numeral
lowercase letter
arabic number followed by parenthesis or within parentheses
lowercase letter followed by parenthesis or within parentheses
Formatting lists correctly supports your efforts to communicate them clearly.
