Finding the best route for you can be a bit tricky because of the size of the dungeon. I will usually only do about half the dungeon, killing as many mobs as I can in 6 minutes. After 5 minutes, make a group in the group finder and leave it. That will leave you a minute to complete your 6 minutes and you will be ported out on the 6 minute mark, ready to reset and port right back in.
Shadowfang is the twink dungeon. You can get a bunch of different valuable twink items here. When soloing at a high level though all items will be level 60, except for in chests. The items in the chests will be around level 20 and those are the ones with the most value. A level 20 Shadowfang will be worth several times what a level 60 one is worth. Bringing a Rogue or someone who can open locked chests is therefor advised.
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I tell you my experience. I'm leveling a priest that it's 60 now and since I have also done some instances (and I have full heirloom set with 20% experience gain bonuses) and been very ahead of the guide, I skipped some zones since they were grey quest for me, well it was a real mess. Missing quests because I didn't to the previous to enable the following. Going in a zone then realizing that I couldn't do that quest because I didn't do the starting quest chain, very unconmfortable. In short what I suggest you it's not to skip areas, or make really sure that you do all the quests required (at least) and check carefully the previous zone you'll going to skip to make sure that you won't have problems with struggling finding where to start the quest chain to sync with the guide section.
This farm almost did not make this list. Even though I have had only a little luck with it, it seems to be gathering some popularity in the gold farming community. Although I feel with the recent changes in 7.3, this farm is very close to dying out. Generally what you want to to do is pull every mob you can as you venture to the last boss in the instance. The only saving grace of this farm (if you can call it that) is that some mobs are GUARANTEED to drop greens. Guaranteed. Whether or not they drop profitable greens is a different question, however it's a must-mention quirk you get from running this instance. It also allows you to get your hands on some rare low level blues.