A meaningful work experience placement while still at school is crucial to a successful apprenticeship, says Ofsted.
The education watchdog wants schools to organise better placements and the government to develop stronger careers guidance for over-16s in England.
In a report, it says official figures suggest around a quarter of the people who begin apprenticeships drop out.
A government spokeswoman said the report gave valuable insights into making apprenticeships more effective.
To pinpoint best practice, Ofsted analysed 15 of the best apprenticeships, among them those run by the Premier League, McDonalds and Sassoons hair salons.
All of the 15 were judged good or outstanding at their most recent inspection. Eight were particularly effective in their work with young people who had not achieved well at school.
All said the most important attributes of a potential apprentice were a good attitude and commitment to employment.
The researchers found that trainees who had completed work experience, course tasters or vocational study were more likely to make better progress as apprentices than people who started straight from school without it.
But despite the benefits of work experience, employers told the researchers the number of students they could accommodate on placements was restricted.
This was because so many schools asked for placements during the same short period at the end of the academic year.
Ofsted's national director for learning and skills, Matthew Coffey said: "There has been much concern lately about the quality of apprenticeships.
"When looking at the national picture we can see that around 70% of apprenticeships are good or outstanding but more needs to be done to improve provision further.
"It is clear that more work experience, vocational study and course tasters are needed to ensure learners are on the right apprenticeship for them and that they understand the demands of work."
Chris Keates, general secretary of the teachers' union, NASUWT, said: "It is ironic that this report highlights the value of high-quality work experience and vocational education at a time when the coalition government has chosen to take an axe to work experience and denigrated vocational education.
"Young people are being let down by this government's vandalism of educational opportunities," said Ms Keates.
But a spokeswoman for the Department for Education said the government was investing £4.5 million over the next two years to give 16-19 year olds in education high quality work experience.
The government was working with the Federation of Small Businesses and other employer groups to review the regulations that can make it difficult for young people to secure good work placements, she added.
Chris Jones, director general of City and Guilds, said better career information was crucial for young people.
"We believe it is critical for the success of the UK economy that after decades of neglect we re-establish the apprenticeship model as an important route to a top career," he said.