According to scientists, how did early people migrate out of africa and into new places?

Our ancestors either left Africa from Ethiopia/Djibouti across the strait to Arabia, or via Egypt to Israel. From there they went, through Iran to India, then down through South-East Asia to New Guinea, which they reached by about 40,000 years ago. Once in New Guinea, they more or less settled and were immobilised by all the other tribes around them. That's why the New Guineans resemble Africans so much. 
They also hooked south to Australia which they reached by about 47,000 years ago. 
They also went from India north-east into China. From China they went up over the Bering Straits and down to the end of the Americas. They also went east from China across the Pacific Ocean, curling down from Tahita and Hawaii, reaching New Zealand as the last place on earth to be reached by humans, only about 500 years ago. And they also hooked north-west into Europe.  (hope this helped cx)