Rubbish In, Rubbish Out

There is an old saying in computing: "rubbish in, rubbish out".  The same goes for keywording and captioning. If your keywording goes awry, perhaps the real reason is in the poor metadata you supplied in the first place. 

Generally speaking, keyworders aren't mind readers, whether they are on staff or in outside companies.  That means they are unlikely to be able to identify every species of bird, or know every city or building in a particular country.  So rather than risk them guessing wrongly, or not including the information at all, make sure all metadata supplied is as full and accurate as possible.

If research is going to be required, you should let the keyworder know where to find the best sources of information, preferably on the internet.

You can also save time and money by getting the language, grammar and spelling correct, particularly spelling of names.  There is usually no spell check for people's names, even those of celebrities, so the onus has to be on the photographer/videographer or photo library to get such details correct in the first place.

If you feel that photographers/videographers can't get it right in the first place, you may find that having someone to collate the information and fix up basic errors will produce a better result than waiting until the keywording is halfway through.

In terms of formatting, try to supply metadata in a spreadsheet, or better still in the IPTC fields of the images. This will make it easier to ingest the information into keywording software, and avoid being charged for extra admin time.  Handwritten notes or unclear photocopies (even in PDF form) are bound to cause problems, so avoid whenever possible.