If I were to attempt to write in exactly the style of those long-ago authors, I would end up with an inert pastiche that would neither attract nor hold a modern reader. I therefore try to convey the flavour of the period in my writing with slight variations of syntax and a carefully chosen vocabulary that avoids verbal anachronisms. If I’m not sure whether a word or phrase was used in the way I want to use it during the regency I double-check. With considerable etymological and historical information, the following are invaluable sources of authentic vocabulary and style.
The Shorter Oxford English Dictionary on Historical Principles 1936
A Dictionary of the Underworld, Eric Partridge 1959
A Dictionary of Slang and Unconventional English Eric Partridge, Reprinted 1982
Captain Grose’s 1811 Dictionary of the Vulgar Tongue gives a fascinating insight into Regency slang and cant, most of which would not have been used in the presence of let alone by ladies; today we would describe it as 'not safe for work'.