For a customer I was looking into custom search results and I really was not aware of how to do it, yeah yeah...
So below you see a custom search result and in the search box some stuff to search for. The Microsoft site says:
The search service interprets the space between terms that use different properties as an AND. For example, if you look for firstname:Ben lastname:"Smith", your search will return results for "Ben Smith," and for any other name that begins with "Ben", for example "Benjamin". The search service interprets the space between terms that use the same property as an OR. For example, if the author property is available for content searches, and you search for author:"Ben Smith" author:"David Jones", the search results will show any item created by either person. To exclude people from your search results, place a minus sign (-) before the name of an identifying property. For example, appending -firstname:"Ben" to your query excludes anyone with the first name "Ben" from your search results. 
The biggest problem of course is that end users will have difficulties with that so it is probably best to build a special searchbox that makes it easier. Will investigate to see if someone has done it before.