Perhaps you already know this but:
Depending on what type of record you're talking about, you can sometimes take the indexing from Ancestry.com and locate the original document on FamilySearch. Sometimes the Ancestry search engine is a little more flexible and better and finding matches. I often take the census page info, or look for a neighboring name and then search again in FamilySearch. Also not all record images available online are indexed. If you go to the catalog, search for the place name and see if the record is available. It may be a different version of the records, so page numbers, etc may not apply, but if the records are somewhat chronological you can still find it.
Initially I only used the search engine on familysearch, but now I always check to see what other records they have online. For example, I've found a goldmine of info in Deeds for New York and Massachsetts. Not indexed in the search engine, but the index images are available online. Takes a little more time, but worth it!