Yes, it can be hard to get into a university, but some people who don't do well (or want to save money) start with a community college for 2 years, and then transfer. I am in the US, and this is what is generally required to get into college:
English - 4 years
Maths - 3 to 4 years
History & Geography - 2 to 3 years
Science- 2 to 4 years
Foreign Language - 2 to 4 years
Arts - 1 year
Electives (classes you choose) 1 to 3 years
With colleges, not all have the same requirements, so if you have an idea of where you would want to go, it would be best to contact them to find out. Does your school have guidance counselors? They can also help you. In the US, we also have to take a standardized test your last year in high school, either the ACT or SAT and you have to achieve a certain score to be accepted. Most colleges require a certain GPA (grade point average) to accept you too, so you have to get good grades.
As far as community service, here is it not a requirement for most public universities, but it would always help your candidature because they like to see people who are involved.
Also for college lectures, depending upon the subject, some of the classes can be HUGE, I had a chemistry class where there were at least 300 people and it was in a giant auditorium. Otherwise, when I had normal classes there were about 30-40 students in each class. When you register for college, you will have an academic advisor that will help you set up all your classes for your specific program. In most cases, they will already have set days/times and you can pick which times (if more than one course is offered) you want to go and fit it to your schedule. Some classes are 1 hour, some can last 3-4 hours, just depends. Then you will get a schedule with all your classes, your professors names, where it is taught (some campuses have more than 1 building), the dates/times and then you usually get a list of your books.
I hope that helps! And if you aren't in the US then just ignore that, LOL.