(i) Never use a metaphor, simile, or other figure of speech which you are used to seeing in print.
(ii) Never use a long word where a short one will do.
(iii) If it is possible to cut a word out, always cut it out.
(iv) Never use the passive where you can use the active.
(v) Never use a foreign phrase, a scientific word, or a jargon word if you can think of an everyday English equivalent.
(vi) Break any of these rules sooner than say anything outright barbarous.
He wrote these for a 1946 essay called "Politics and the English Language", the point of which was to discuss the decline of language in political writing into imprecision and incoherence. His essay would be just as applicable to political writing today, but his rules can really cover any kind of writing, including blogs.
I'd actually add one rule of my own, which is, "read each sentence and paragraph aloud. Reorganize and punctuate accordingly." Too many people write in a disorganized stream of consciousness, which is an easily solvable problem if you just read your own writing back and self-edit.
By the way, when I was in school, kids would often look at rule #6 and take it to mean "break the rules if you think you're smart enough", and of course everybody then did in an attempt to show that they were. When the teacher would call them out on it, they would pretend to be little geniuses who knew more about writing than the teacher and would stand behind rule #6 as a defense.
But the point of the 6th rule is to act as a hedge against the inherent imprecision of the English language, which even Orwell acknowledged. Rules 1-5 are intended to increase that precision, which is the opposite of what flowery language riddled with cliches and jargon does.
His rules boil down to being simple and direct, the foundation for great writing. (My little addition is for the same purpose.)