As an editor, I often follow this rule:

• When you can, change a word to one with less syllables but the same meaning.

I’m also quite happy to follow copywriters’ rules and start sentences with “but” or “and” when it helps to break long, multi-clause sentences into more readable chunks.

So, when I see a sentence starting with “However,” I usually change it to start with “But.”

This can produce some unfortunate repetition, as an author today pointed out to me. Take this sentence:

Not all of these welfare recipients rely entirely on benefits—some combine benefits with an element of paid work—but nearly all are net tax beneficiaries who do not make a real contribution to the public purse. But come election time, as adults they are compelled to vote. (emphasis added)

Here, it’s better to change what would ordinarily be the second “but” to “However,” to avoid repetition.

This shows that while it’s good to have a clear set of rules to edit by, it’s also important to keep looking for places where breaking them makes the writing better.