There is a helpful guide written for each of the specs you're interested in. Check out the first post in the blood and frost threads. If after reading those you have further questions, or there's something you don't understand, then this thread is a good place to ask for clarification or explanation.
Hello. Im playing WoW for a long time, but never play DK. It's all because i always cant understand the basic rules of right use runes, i mean what i should seek doing rotation (as frost and as blood). Thank you