There is a lot of advice people are eager to give soon-to-be freshers: drink sensibly, practise safe sex, develop an independent work ethic. Then there are the things they don't tell you about, such as fat fresher syndrome.

Unleashed into the world of takeaways and cheap pints, and in charge of your meal planning possibly for the first time, you could end up eating too much junk, and arrive home at Christmas a little porkier. It might make your mum happy (her greatest fear is that you'll waste away), but it won't make you feel good.

So, during freshers' week, when they give you the tour of the university gym, pick up the leaflets and tuck them in a drawer for term two, when you might have some calories to burn.

Listening to the experiences of older students may prove illuminating. Nelly Colmer, a fine art student at Central St Martin's in London, says: "For the first time, you're in charge of your life and routine, and you don't have anyone telling you what to eat or do. When you get your head around that, it's an enjoyable process, making your own meals, going food shopping and budgeting for the week.

"It's easy to snack all day instead of eating proper meals. [But] we have really good restaurants and cafes. It's all home-cooked stuff. Most people eat a big lunch at college, and that will be their main meal of the day."

Natasha Rosenbaum, a history of art student at Sussex University, says: "Take vitamins and echinacea, eat fruit and vegetables, and make sure you get enough sleep. All my friends have had lots of colds. If one person gets it, it goes round your house when you're all sharing towels and plates and stuff."

During her second-year exams, Rosenbaum was struck down with a horrible case of tonsillitis. "I lay in bed for a couple of days trying to get rid of it, then went to the GP. The doctor was really, really nice. I also saw a student adviser, who was helpful. They told me the procedure to have illness taken into account by the markers; it involved a mitigating evidence form. And I was allowed to take one paper home."

Sometimes it feels as though the entire point of university is to get you drunk and, indeed, there are industries aiming to do just that. At my university, it was all about tequila nights and Red Bull-and-vodka nights, with 50p shots and St John's ambulances parked outside. Tony Downes, pro vice-chancellor at the University of Reading, recently accused local pub landlords of "irresponsible promotional activities". In an article for the Guardian, he wrote: "The worst of these was when a bus was parked outside a hall of residence, in a residential neighbourhood, for the purpose of handing out free beer."

Colmer says: "What I've noticed is that the first-year people go mad and drink every day. [Then] they suddenly have a panic attack and think 'oh my God, I'm a bit of an alcoholic'. Maybe they embarrass themselves a few too many times. It's important to have fun, but it's also good not to rely on alcohol to give you confidence."

You'll be bombarded with information about safe sex in freshers' week. There's no evidence that students have more unprotected sex than other young people, but there's a captive audience of sexually active young adults on campus. The Health Protection Agency says men aged 16 to 24 account for 57% of male chlamydia diagnoses, and women of the same age group account for 75% of all female cases. For gonorrhea, the same figures are 39% for men and 70% for women.

A startling survey of 2,200 students, carried out by the Terrence Higgins Trust and the National Union of Students, found that more than one in 10 cannot put a condom on properly, and 16% believe two condoms are safer than one. More than a third of students believe condoms have holes in them big enough for HIV to get through.

Lisa Bartlett, a manager at Brook Advisory centres, which offer sexual health advice and treatment to young people, says: "For people who are not entirely sure of their sexuality, going to university is a great opportunity to get the space you need to be true to yourself in a way you perhaps haven't been able to at home."

Every university has a lesbian, gay, bisexual and transsexual society, and many university towns also have an active scene. The most important thing, Bartlett says, is that people are clear about what they want to do. "Take a little bit of time to think about boundaries you have, and keeping yourself safe. You're with people you don't know - be cautious about the situations you're putting yourself in. Take the time to chum up with someone and look out for each other."

Reputations are made quickly in freshers' week and university is a hub of gossip, so be aware of how you want to project yourself, she says. And carry a condom.

Practically all universities have on-site student health services, where there's likely to be a GP as well as a nurse who can prescribe contraception. One student says: "You don't have to have a long-winded session - you can get it really easily and it's free." Then there's the real reason why you're at uni: the degree. The biggest leap many new students find is to university-level work. Rosenbaum says: "University is slower than A-level. You don't get work every single lecture. It is hard to adjust and get motivated to do stuff." Her advice? "Do the reading. Go to everything - all the introductory stuff. That will set you up. A lot of people didn't bother with introductory lectures - they had no idea what was going on."

If you feel as though you're sinking at any point, get help. The last thing a university wants is for you to fail and drop out. For Colmer, it was only at university that her dyslexia was properly recognised. "For the first time, I got loads of help and that was the most positive thing," she says. "My dyslexia was taken seriously and they gave me equipment to help me do better in my course. I even got extra tutoring, one-to-one, an hour a week."

Your union will help you access tutoring, counselling, financial advice and support if things aren't coming together. That's what it's there for - and it's also a good place to start meeting people.

What just about everyone will say to you is: take your time. Nothing gets set in stone during freshers' week. Colmer says: "For the first year, don't stress too much. You've got time to get your head down and get settled, especially if you're outside your comfort zone and it's all new. It's not just a degree you're doing. University is a life lesson - you are learning about being an adult and becoming the person you want to be."