Some 54% of A-level candidates with conditional offers say they have not thought about what to do if their results are poorer than expected.
Almost three-quarters of applicants (70%) have not researched the clearing process for unfilled degree places.
Of these, 939 were holding conditional offers of places, dependent on their A-level results next week.
Just under half (48%) said they were confident they would get the grades for their first choice.
More than four-fifths (82%) said they had an insurance choice as back-up - but 40% said they did not want to go there.
A quarter (23%) had an insurance offer with the same or higher entry requirements as their first choice.
Overall, 54% of those questioned said they had not made any preparations for the possibility that they might not get the grades for either their first or second choices.
Last year 12% of applicants got their places through clearing, but the survey reveals some misunderstanding among this year's students of how the system works.
Some 54% wrongly think that if they do not get the grades for their first choice, but do get their insurance choice, he or she can still apply for another course through clearing.
In fact if a student in this position wants to take their chances in clearing, they would have to give up their second choice university place, something Which? University advisers say can be risky and stressful.
Ms Sodha said: "As A-level results day approaches, it's an understandably stressful and nerve-wracking time for prospective students, especially those who aren't confident they'll get into their first choice university.
"Hopefully they won't need a back-up plan, but we advise they research all their options just in case."
Nick Davy, higher education policy manager at the Association of Colleges advised applicants to explore credible alternatives to a three-year full-time academic degree before results day.
"These can include full or part-time higher education offered by colleges, which is often cheaper, and a range of professional certificates and diplomas such as marketing and accountancy.
"There's also the option of an apprenticeship or higher apprenticeship in a range of occupations.
"Students need to weigh up what their employment prospects will be after degree study against the debt they will accrue and seriously consider what an alternative educational and training route may bring in terms of expense, career progression and financial rewards."
Source: Bbc.com
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