It can be hard to keep status messages to 140 characters or less (or a 116 character message if you've included a link). I realized recently that I follow the same algorithm to bring it down to size every time, so I thought I'd write down my steps. Maybe the process can even be automated?
These steps are in order. If the tweet is under the character limit after a step is completed, there's obviously no need to continue to the next one.
1. Eliminate Oxford commas.
I'm in favor of the Oxford comma as a way to bring clarity to sentences with multiple clauses, but they take up valuable space. Every comma counts, and there are other ways to clarify your sentence construction.
2. Remove non-essential adverbs.
Adverbs can be essential modifiers that allow you to fine-tune the message you're conveying (usually, locally, here, there). They can also be used to convey the writer's emotional tone (really, extremely, very). While removing the second set will change the tone, it won't materially change the underlying meaning of the sentence. In fact, many writers would probably argue that it will result in a clearer sentence.
3. Replace "and" with an ampersand.
The ampersand - & - is only meant to be used in informal situations. What could be more informal than a tweet?
4. Change written numbers to Arabic numerals.
Written numbers and numerals aren't interchangeable: consider the sentence "4 score and 7 years ago", which carries less gravity, despite being functionally identical. Commonly, numbers under 10 are spelled out. This rule isn't hard and fast, however, and can be suspended in the context of a tweet. Again, the meaning of your message won't be lost. Note that this doesn't mean you should replace numerical homophones with numbers, which is an easy way 2 lose respect from your readers.
5. Use common abbreviations.
Just as you lose some gravity by replacing written-out numbers with their symbolic equivalents, replacing "with" with "w/" gives your tweet the quality of a hastily-written note. Nonetheless, "w/" (with), "w/o" (without), "wrt" (with respect to) and "b/c" (because) will save you a handful of characters. You can save more by using "eg" (exemplī grātiā, which means "for example") and "ie" (id est, or "in other words"). I lightly bend grammatical rules by omitting the punctuation marks that should normally be present in e.g., i.e., a.m. and p.m.
6. Rewrite your tweet to use shorter sentences.
Consider the sentence "I was going to go see Star Wars, but it was sold out, so I ended up seeing The Big Short instead" (96 characters). You could rewrite this as "Star Wars was sold out. I saw The Big Short instead." (52 characters). By doing so, you've saved 44 characters that you could use for a short review or a link. There's nothing wrong with using several shorter sentences in place of a longer one. If you wanted to be fancy, you could use a semicolon instead of a period. Just remember Kurt Vonnegut's take on them: "They are transvestite hermaphrodites representing absolutely nothing. All they do is show you've been to college."
7. Screw the rules.
The final option is to proudly reject the 140 character limit. Writers like Marc Andreessen do this with a construction called a tweetstorm: a series of tweets, where each post is written by hitting reply on the previous one. Twitter threads them together into something like a blog post. There's another option: because I tweet using Known, I can keep writing, and the end of my tweet will turn into a link to the full text. However, both of these options are an inconvenience to the reader, and should only be used if there's no way you can limit your message to a single post.