In general I would agree with C. Browning. I think that is all in all the best advice for most magicians. But that is also for guys who don't have a specifically developed character. For people with very specific characters, however, I think Johnny Butterfield hit it right on the head. Gazzo wouldn't be Gazzo without a foul mouth and a lower class accent. Now look at Richard Turner. This isn't meant to big a big slap at him(he is by far my favorite of the demo guys) but he has a character that would actually benefit from not sounding so well pronounced and proper. Indeed a wild west gambler character would do well to peruse through old dime novels from the era. Think of the difference language alone made between a movie like, "The Assassination of Jesse James..." and "3:10 to Yuma." Both good westerns but one is practically a modern day classic and I honestly think the dialog played a huge role in that.
There's a truth to this but I think I mentioned that there is a huge difference between the Character the public witnesses vs. the person that must juggle the business side of things. I'll likewise point out that looking at the exceptions and thinking they give you permission to be lethargic ain't the wise bet. If you're in this craft for the sake of putting dough in your pockets you need to look to the rule -- the standard that seems most constant in our universe, which goes straight back to what I mentioned earlier.
When I was doing the Punk Rocker street performer a few decades ago (I was probable about the age most here are today -- early 20's) My language habits were all over the place WITHIN THE ACT but not when it came to actually talking with would be job leads. These people should expect RESPECT and when you give it to them they are far more likely to give it back in way of work, referrals, and positive recommendation letters.
Though my introduction to proper enunciation came early in life the value behind it came through my work in side-shows (before they were in vogue and still under canvass) in that you had to be understood by persons from every walk of life. Too, you had to be able to make the pitch 18 or more times a day (the shows started at 9 in the morning and ended between 10 and 11 in the evening, no "breaks" they were continuous) learning to pace yourself and focus on how you spoke was part of the "trick" to not wearing your voice out and keeping it strong.
When it comes to the stage persona itself, which I think was the key question here, the answer is likewise found in traditional theater. . . while magicians claim to be actors playing a part very few ever learn anything about acting or proper theater, if some of our books books actually emphasized these things more than card tricks I think the craft would know a seriously different kind of reputation in the public mind. Nonetheless, you will find that any and all characters you do must have part of you inside them. Oddly, even when you're "just being yourself" on stage or in front of folks when clowning around, you will channel a bit of ham. . . you must if you are to be ENTERTAINING with the former being just as valuable for the very same reason.
Go see any film by Mel Gibson, Tom Hanks or Jim Carey and tell me you don't see them playing the same character over and over and over but with slightly different plot-lines. It's exceptionally rare you do not see this in the majority of actors and the rolls they get "typed" into. Tom Cruise has two films in which he's not playing Tom Cruise;
Interview with a Vampire and
Collateral they are the only two of all of his films that are distinctly distant from most roles he takes on and the reason is that he puts a greater level of his own self-image into the other roles and so things get repetitive. . . similar in action, plot and gesture.
There are those in the acting world, who seem far more flexible such as Johnny Depp, but they are few and far between -- exceptions, not the rules. You will also find that the majority of those that fit this mold aren't just in film but likewise live show actors -- theatrical thespians to the core, which is why they have such strong versatility.
Eostresh has made another point however, when it comes to the persona being played and wordage; we need to adapt a mode of speech that fits the entity. . . Capt. Jack Sparrow wouldn't be the lovable lush we love if it weren't for his peculiar way of saying things, would he? The new character I've been experimenting with the past five or so years steps a bit outside my comfort zone but MUST because he has to have that turn of the century bravado that was so common to the late 19th and early 20th century in the show-biz (variety arts) element (trust me, if you ever hear a recording of Barnum or Houdini, it will make you wonder how they ever became so highly acclaimed), but for Phineas VanBirch, Esquire a world traveler, inventor and professor of the the Surreal, Strange & Esoteric it is paramount that he be able to mirror the ways of that particular time and persona -- that half-shyster/half-intellect that was so common to the day. This "stretch" however, is what acting is all about and what character creation (even when you are just being you) is all about.
BTW... "Being You" on stage is typically more about being who you think you are and how you want to public to see you, not who you really are in life, even when you want to believe otherwise.
It takes time and experimentation to create a genuine character, it also means being willing to listen to others and accept guidance... coaching and direction by persons that know theater first and foremost followed by those that can aid you in the more technical aspects of magical technique and gesture. This is the combination that will give you the success I'll assume most of you wish to know.