I have a sort of tier list of how I utilise caps and Italics.
"for when I'm whispering" Italics, No Caps aside from names or referring to one's self as 'I'
"For when I'm talking Quietly" Caps used as needed and in Italics, but will add additional caps when to bring emphasis to a word when the sentance is all Italic.
"for when I'm muttering" No Caps aside from names or referring to one's self as 'I'
"For when I'm talking normal" Caps used as needed.
"For when I need to, ye know, emphasise a certain word"
"For when I need to Emphasise a certain word a little stronger than normal" I would use a capital letter to add a little extra power to the word.
"For When I'm Talking A Little Louder"
"WHEN I'M SHOUTING!" I would use sparingly. Don't construct entire speeches this way. You can emphasise those words too by using Italics.
"Another thing I do is, well... hmm, how should I put this, its perhaps a little unconventional? maybe? See, the way I use commas and fullstops when someone is talking is, that I'd put a comma every time someone takes a breath, or when I needed a moment to think of my next sentence. Speaking along with your characters out loud or even in your head can help you understand when and how to use them. For a short pause you'd maybe use a comma, and for a longer pause, a full stop. And another thing I do, which may have already sparked some controversy as I just did it right now. I used the word 'And' after a full stop. The reason I did that is because at the time, I thought I had finished talking, until I realised I hadn't talked about this part yet. It may not be one hundred percent correct according to professor Oxford Dictionary, but most people don't speak in perfect grammar. So why should your characters?"
Now on the subject of irregularities. I'll confess that my only writing experience is for online fan fiction sites. So I'm by no means a pro, but I'll offer help, and it's up to you guys to decide if my method is worth adopting or not.
Back to what I was saying, The story I'm writing is about the game Skyrim. A video game where your character has a special power known as shouting in the Dragon's language. Basically you say magic words that can cause deviation where ever you're facing.
When a character shouts like that, its a thunderous Boom that comes from their voice which is unique to them. Therefor, I make the words illustrate that.
"Dragons Shout Like This!" Caps for the first of each word and in Bold letters so it stands out and demands to be seen. Perhaps not the prettiest to look at on a page, but it's a personal choice.
You will notice that I don't make a habit of pulling out "ALL THE EMPHASIS TACTICS AT ONCE!"
Because, how do you top that if you need to go Bigger? Or how would you emphasise a particular word out of the sentience?
"YOU COULD try THIS!" But did the word 'try' look like the word I was trying to draw your attention to? Or did it look my voice broke midway through screaming at someone?
When it comes to dialogue in general, I often use double quotations.
"When I talk, I read like this"
And I use single quotes when a character is quoiting someone in an unspoken sentence. Narrating, in other words.
If you recall when I said 'When I talk, I read like this'. Only this time I Wasn't talking. I was internally quoiting myself, or for the sake of arguing, quoting someone else.
If you were to quote me verbally in a sentence, you'd maybe say, "He was yammering something like, 'When I talk, I read like this', but I wasn't listening anyway, because I have potatoes in my ears"
You also have words put in your mouth :P
Moving on from my hilarious jokes, one thing I don't suggest doing is using single quoits if your dialogue is All a direct quote of someone. Because then it looks like this,
"'And triple quotation marks aren't pretty'" If you were going quote someone entirely, maybe make use of Italics instead. But be wary because it might come off to the reader that the speaker is mocking the character they're quoting.
I can't for the life of me think of an example for that one... sorry.
Just be creative. But do your best to be consistent in your writing.
Remember, writing like all art is about self expression. You can copy the big names's style or you can make note of them as a guide but also look for your own way of doing it.
Hope something my lessons helped in some way, because I'm an hour late for bed over it. :/