The Elements of Style

While reading "The Elements of Style" by William Strunk Jr. and E.B. White I ran across some very helpful rules/tools for me to imply in my own writing. One being found in "Elememtary Rules of Usage" article 10. This shows how to determine if who or whom is necessary. I have always had a difficult time with that and I just found myself sometimes using one or the other, just to mix it up a bit. Within the section "An Approach to Style" I found article 2, "Write in a way that comes naturally" to also be very beneficial. When writing an essay or paper for school I am always concerned that I added too much "naturalness" to it, that it is too similar to my own personal form of writing. I was put at ease while reading article 2 when the authors state "...using words and phrases that come readily at hand." and "...when you write in a way that comes naturally, you will echo the halloos that bear reapeating".
Although there are many helpful tools in "Elements of Style" there are also some that went aganist other rules I have been taught. In the numerals section found on p.34 states that you "do not spell out dates or other serial numbers". The only exception given for this is when "they occur in dialouge". I was under the impression that there was some rule stating when using numbers in text you should put the actual number, for instance 3, if the number is between 1 and 10 but spell the number if it is higher. I very well be mistaken or mixing the whole thing up, but I know I was taught that somewhere down the line. There had also been a debate about whether or not a comma is needed in a list after the last thing mentioned, before the "and". I used to think it was necessary to write "red, white, and blue" this way, but I was told that is incorrect. I was told that "red, white and blue" is the proper way. On p.2 of "The Elements of Style" it states that "In a series of two or more terms with a single conjunction, use a comma after each term except the last". This, to me, sounds like the very thing that I noted as being correct, but the example on p.2 shows "gold, silver, and copper" written that way. The only exception to the rule states that "In the names of business firms the last comma is usually omitted". An example for this is "Donaldson, Lufkin & Jenrette".