The way to 45 will share the same places with 30th to 39th. And I will continue the introduction where I stopped last time.
Get off from the Menethil Harbour in the wetlands and ship to the Salamo. You will be immediately assigned with 2 quests, which belongs to 2 different series. Upon your fulfillment of one quest, you will be sent to the Blizzard duke. And do not send the quests back at once. Continue with your quests to 40 and then you can send it back to the Blizzard duke. When in your way back, you can by the way accept the quest of the crown. The skill of summoning war-horses is of great magnitude. Finish all the quests in the city and outlands will bring you to 42.
At the same time, you can fulfill the quest in the Stromgarde and Faldir's Cove which belong to the Hillsbrad Foothills. And also put an end to the quests in the Alterac Mountains. The quests in the Hinterlands are not so difficult to deal with so you can deal with them by the way. The Stranglethorn Vale has contained inside many quests for you. Go and fulfill them, you will upgrade to 45. Now there will be another new map for you.
The quest in the Scarlet Monastery is worthy your attention since from the Locations in the reward of your fulfillment will be the biting bone axe, which is so rare and unique. 
And the places for 45th to 50th rating are in Tanaris, Philaster, Hinterlands, and searing gorge.
When in 45th, you can firstly accept the quest requiring you to fetch the Shrieker's soul in the Tanaris, together with the Wastelands justice and the Waste wander Bandits, a series of quests. Now you will be in 46. In such period, you can commit the undercity quests. The possible reward of ring will help you much.
Now you can go to Philaster to have all the quests. Besides the quests of attacking the Titan and the water element etc along the seacoast, you can finish all the quests which handed from others. Remember to collect the egg of Hippogryphs when you are in the way of finishing the snowman quests.
When all of these are finished, you are now 48. Go ahead and pass on your quests. Now you can go ahead to Hinterlands, Philaster and Tanaris. And the fulfillment of all these can bring you into the 50th rating.

WOW power leveling - When you first start a game of World of Warcraft, you will be taken to your race's starting area. All the races except trolls and gnomes begin in a unique location. Those two races have to share starting locales with the orcs and dwarves, respectively. After watching a brief in-game cutscene introducing your race, you are set loose upon the world.