What is the benefit of setting the text field to lower than 60 characters?
Concordance will set aside X number of bytes of memory for X number of characters in a Text field (A paragraph fields only takes as much memory as it needs, all words are indexed into the dictionary files). Thus, even if you only enter in 5 characters in a Text field, the program still sets aside 60 (or whatever limit) bytes of memory for that record in the .KEY file. This is typically only significant if you have massive databases or memory constraints on your network.

If you are not sure whether to set a field as an Index or Key field can you set it to both?
You can mark any field as Key, Index, or both. Key field searches run faster because the Key file is essentially a smaller version of the dictionary files. If you mark too many fields as Key, it defeats the purpose of having the Key file. You can perform a relational search on paragraph fields, but it will only search on the first 60 characters of the field. Any field can support relational searches, however, relational searches will work better on numeric, date, and fixed length text fields. These fields are marked as Key by default. Full text searches always search through the dictionary files (.IVT and .DCT).

When I conduct a simple word search it is very quick, but when I use relational operators it seems slow. Is this normal?
Relational searches are slower because they require comparisons across the database and/or field. Speed of the searches is dependent on the type of search you are doing. You can also adjust the Dictionary Cache under "Tools| Preferences| Indexing" to optimize your workstation's search performance. The default Dictionary Cache is set to 2 MB, it can be increased to 8 MB (ex: CPU 128 MB of RAM, Indexing Cache and Dictionary Cache 70 MB and 8 MB, respectively).

Can a paragraph field that is only indexed have relational searches performed on it?
You can perform a relational search on paragraph fields, but it will only search on the first 60 characters of the field. Any field can support relational searches, however, relational searches will work better on numeric, date, and fixed length text fields. A relational search will also work faster on fields that are marked as Key fields. Please review the section on "Searching" in the manual for more detail.

How do I search for documents where a field is blank?
Perform the following search [FIELDNAME = ""]. FIELDNAME is the name of the field you're searching, and "" [quote quote] has no spaces between. As with any relational search, be sure to include the spaces around the equal sign operator.

I can't find a particular word or letter I'm searching for, even after reindexing.
Concordance maintains a Stopword List. These are noise words that are skipped during the index process. This list includes letters of the alphabet. The word you're searching for is most likely on this List. Click "File | Dictionaries | Stopword List" to change the Stopword List to your specifications. Then, run a complete index ("File | Index") to rebuild the dictionary including your Stopword List changes.