The best way to run a low level character to Booty bay is this:
First, get a mage to port you to Dalaran and set your hearthstone there so you can easily get back.
Then, return to Stormwind and run south towards Stranglethorn vale. As soon as you can, engage a mob and let yourself die. Run the rest of the way to booty bay as a ghost. You can run over water so don't feel you need to follow the road. When you get to booty bay, take the boat to Ratchet. When there, visit the graveyard and resurrect. Take the boat back to booty bay and you're in business. NOTE: Do not resurrect at the graveyard just outside of Booty Bay - this returns you a graveyard near Stormwind and you'll have to do it all again.
The best way to run a low level horde character to Gadgetzan is this (this one takes slightly longer as the trip south is further):
Get a portal to Dalaran and set your hearthstone there. Return to Orgrimmar and head east until you meet a mob. Again, let yourself die. As a ghost, head east to the coast and run south over the sea, taking care to not get fatigued. When you get to Tanaris, deliberately run out into the sea and let yourself fatigued until you die again. You'll reappear at the graveyard near Gadgetzan. Resurrect and run to safety and the neutral AH.