We all know the obvious, capitalize the first word in a sentence, proper names, etc.; but, there is one area that is a bit confusing for some writers (and this one included): Do you capitalize the first word of an unspoken thought?
The rule is simple: Yes. If words are directed by a person to himself or are merely unspoken thoughts, capitalize the first word but do not use quotation marks.
I thought to myself, When is all this going to end?
He said to himself, Here we go again!
Another area of some confusion may be the use of personal titles such as lord, king, president, etc.
The rule: Do not capitalize words indicating position or occupation when they are not used as titles.
I am just one of many secretaries.
The architect, Riley, and the treasurer, Chuck, were always at odds.
Do capitalize titles used in direct address expect when they can be applied to a wide class of people.
Please give a warm welcome to Lord Hargrave.
Yes, Your Honor, I understand.
Yes, sir, I will get on that right away.
Listen carefully, gentlemen, to this tale.
Do not capitalize a title not followed by a proper name unless it is a direct address.
My uncle is a director of motion pictures.
The judge said not to do that.
Your sister is hot.
The lords of the land rode into battle.
These are but a few rules for when to capitalize and when not to capitalize. I hope this helps to clear up some confusion.