One must strive to imitate the language of the Bronte sisters and others of that ilk. Using a dialect is more likely to be credible.
Use the "thou" forms instead of "you" when addressing one family member or lover.
Use modals like shall, may, will instead of some continuous forms:
eg Will she come?

Just to explain the meaning of the grammatical term "relative clause":

As you may know, Santa is spending this Xmas down-under visiting relatives, leaving the prezzie handout to DHL. Unfortunately it's been very wet down-under (despite being mid-summer), and Santa with his family (all those little subordinate Clauses) have been cooped up in a beach-bach with his relative Clauses, and all the wet and bedaggled reindeer, all suffering from cabin-fever listening to endless downpours and gales outside. Some of the little Clauses have in fact become quite insubordinate and objectionable (Santa calls them 'object Clauses'). Mrs Santa has been trying to organize indoor games and activities to keep everyone amused: Santa calls her a 'co-ordinating Claus', whilst he himself is of course the main Claus

http://books.google.com/ngrams/graph?content=has+been+wanting%2Chave+been+wanting%2Cis+loving%2Care+loving&year_start=1500&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Chas%20been%20wanting%3B%2Cc0%3B.t1%3B%2Chave%20been%20wanting%3B%2Cc0%3B.t1%3B%2Cis%20loving%3B%2Cc0%3B.t1%3B%2Care%20loving%3B%2Cc0

Well this whole thing started because of the MacDonalds ad "I'm loving it", which to me is borderline - not something I would say.

What surprises me is that 'have/has been wanting' has declined so much lately

"Because back in the 1840s, around 80 percent of people living in Wales were Welsh speakers, many of them spoke no English at all. Fast forward to the recent 2011 census and that number has dropped to below 20 percent."
as stated in :
http://sabotagetimes.com/life/mind-your-language/

Not sure whether this is well-founded or not, but if so could account for the late rise in continuous forms

http://homes.chass.utoronto.ca/~cpercy/courses/6362-lamont.htm

My next question would be: how much did the post-1847 drive to teach English to Welsh children in schools contribute to the much-more-widespread use of continuous/progressive forms?
Did these forms become more common in 1800's because of grammarians' influences, the crossover from Welsh or upper-class affectation with over-politeness?

Either way it seems that the true Englishness of today's widespread use of continuous forms is questionable

http://books.google.com/ngrams/graph?content=is+coming%2Care+coming%2Cam+coming%2Cwill+come%2Cwill+be+coming%2Cis+going+to+come&year_start=1500&year_end=2012&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cis%20coming%3B%2Cc0%3B.t1%3B%2Care%20coming%3B%2Cc0%3B.t1%3B%2Cam%20coming%3B%2Cc0%3B.t1%3B%2Cwill%20come%3B%2Cc0%3B.t1%3B%2Cwill%20be%20coming%3B%2Cc0%3B.t1%3B%2Cis%20going%20to%20come%3B%2Cc0

http://books.google.com/ngrams/graph?content=will+come%2Cshall+come%2Cmay+come%2Cmight+come%2C+will+be+coming&year_start=1500&year_end=2008&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cwill%20come%3B%2Cc0%3B.t1%3B%2Cshall%20come%3B%2Cc0%3B.t1%3B%2Cmay%20come%3B%2Cc0%3B.t1%3B%2Cmight%20come%3B%2Cc0%3B.t1%3B%2Cwill%20be%20coming%3B%2Cc0

Do the above really chart the rise of continuous forms in English?
Do they really show a decline in the use of straight modals (esp shall) in favour of continuous?
Did the form "will be coming" really begin as just a Victorian affectation?

"deviation" + "railway" shows up quite easily on Google

I never understood why the French for 'detour' is 'deviation' on all the roadworks

So what did they use in Middle English for "decide"?
"Choose" is not quite the same thing.
"betake" seems little used in books (after 1500)

"slit" (cf schliessen, entschliessen) does not seem to be used in this meaning in OE

http://books.google.com/ngrams/graph?content=decide%2Cchoose%2Cchose%2Cresolve%2C+betake&case_insensitive=on&year_start=1500&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t4%3B%2Cdecide%3B%2Cc0%3B%2Cs0%3B%3Bdecide%3B%2Cc0%3B%3BDecide%3B%2Cc0%3B.t4%3B%2Cchoose%3B%2Cc0%3B%2Cs0%3B%3Bchoose%3B%2Cc0%3B%3BChoose%3B%2Cc0%3B.t1%3B%2Cchose%3B%2Cc0%3B.t4%3B%2Cresolve%3B%2Cc0%3B%2Cs0%3B%3Bresolve%3B%2Cc0%3B%3BResolve%3B%2Cc0%3B.t1%3B%2Cbetake%3B%2Cc0

http://books.google.com/ngrams/graph?content=wanted+him+to%2Cwanted+her+to%2Cwant+him+to%2Cwant+her+to%2Cwant+you+to%2Cyou+should%2Cwant+thee+to%2Cwanted+thee+to%2Cthou+shouldst%2Cthou+shouldest%2Cwant+ye+to%2Cshe+should&case_insensitive=on&year_start=1500&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cwanted%20him%20to%3B%2Cc0%3B.t1%3B%2Cwanted%20her%20to%3B%2Cc0%3B.t4%3B%2Cwant%20him%20to%3B%2Cc0%3B%2Cs0%3B%3Bwant%20him%20to%3B%2Cc0%3B%3Bwant%20Him%20to%3B%2Cc0%3B.t1%3B%2Cwant%20her%20to%3B%2Cc0%3B.t1%3B%2Cwant%20you%20to%3B%2Cc0%3B.t4%3B%2Cyou%20should%3B%2Cc0%3B%2Cs0%3B%3Byou%20should%3B%2Cc0%3B%3BYou%20should%3B%2Cc0%3B.t4%3B%2Cwant%20thee%20to%3B%2Cc0%3B%2Cs0%3B%3Bwant%20thee%20to%3B%2Cc0%3B%3Bwant%20Thee%20to%3B%2Cc0%3B.t1%3B%2Cwanted%20thee%20to%3B%2Cc0%3B.t4%3B%2Cthou%20shouldst%3B%2Cc0%3B%2Cs0%3B%3Bthou%20shouldst%3B%2Cc0%3B%3BThou%20shouldst%3B%2Cc0%3B.t4%3B%2Cthou%20shouldest%3B%2Cc0%3B%2Cs0%3B%3Bthou%20shouldest%3B%2Cc0%3B%3BThou%20shouldest%3B%2Cc0%3B.t1%3B%2Cwant%20ye%20to%3B%2Cc0%3B.t4%3B%2Cshe%20should%3B%2Cc0%3B%2Cs0%3B%3Bshe%20should%3B%2Cc0%3B%3BShe%20should%3B%2Cc0