Earlier quoted context omitted.
Depends on the corpus. If your problem fits a conLL task, you can read lots of papers about it. If you can build on an existing wikipedia entity/relation graph, dictionary, gazzette that's a big boost. For academic research papers, look at citations for your input stream then SVM tf-idf bigrams. If sentiment/quality analysis, that's another tack
Right now I'm hoping to extract entities and relations between them to use as facts for relevant domain specific search and validation. Reading up the articles, YCombinator included: https://blog.ycombinator.com/how-to-get-into-natural-languag...
http://xren7.web.engr.illinois.edu/www17-StructNet-part1.pdf
http://xren7.web.engr.illinois.edu/cikm16-profile.pdf
Also solr/lucene/elastic indexes are good tools for filtering your inputs and deciding what the unit doc will be (sentence, paragraph, numbered section of research paper etc