Punctuation affects searching, so you need to decide on conventions for things like commas and periods. For example, "A H Smith and Co" will not be recognized as the same term as "A. H. Smith and Co."

As with the other conventions, try to be consistent about how you punctuate terms. Standard authorities will have their own conventions. If you're creating your own vocabulary, try to stick to rules used by a standard authority. AACR2 contains one set of rules for punctuating people's names \and place names.

Diacritics (umlauts and acutes and other accents from non-English alphabets) seem to be a bad idea for ARGUS at the moment, as they don't get matched by ordinary characters when you search. As Sean Connery might have said, in The Hunt for Red October, "Thingsh in ARGUSH don't react too well to diacriticsh."

If you think your users will be often trying to type in a term with different punctuation from the style you have chosen, you can create that different version as an alternate term.