Sometimes students feel the need for extra help in a course, beyond what's provided by the course instructor and the teaching assistants. One way of getting help is to hire a private tutor -- a knowledgeable person who isn't part of the official course teaching staff, whom you pay usually by the hour for coaching, usually one-on-one but sometimes in small groups.
The first thing to say about this is that we hope you won't find it's necessary. A private tutor is expensive, and you should make sure you've been to your classes, consulted your instructor and your TAs at their regular office hours, attempted sensible extra work on your own, and so on.
The next thing to say is that it's a bit of a jungle out there. There are some really excellent private tutors, and there are some who are just in it for the money. Your instructor may be able to help you advertise for a private tutor -- usually by posting a note along the lines of "I have a student who needs a private tutor in my course" on an appropriate newsgroup -- but neither your instructor nor the department as an institution can recommend particular private tutors.
A good private tutor offers you help in understanding the difficult ideas in your course. In computer science, this means explaining language constructs, working through specific examples, getting you to do examples and helping you fix them until they work, looking at old assignments and tests in the course, and so on.
Private tutors who do this kind of thing well may very well be hired as regular TAs later on. In fact, some of them know how to do it because they are regular TAs -- though of course we do not want someone who is currently a TA in your course to be your private tutor. Even if you're in a different tutorial, this would still have at least the appearance of a conflict of interest.
There definitely are good private tutors, and we do not at all want to discourage you from working with such a person if you feel the need.
A bad private tutor writes your assignment for you.
A private tutor who coaches you in detail through an assignment solution is still doing a bad thing, and if you let your private tutor do that, then you are committing an academic offence.
If your prospective private tutor offers to help you with an assignment, find another private tutor. If your actual private tutor offers such help, express your fear of committing an academic offence and ask to work on a similar but distinct assignment from a different offering of the course.
If you see an advertisement posted by a private tutor that mentions your current assignment, don't even bother contacting that person.
We're not in the business of advising you on how to commit academic offences successfully, but consider this, if someone wants to sell you an assignment solution and promises you're the only one getting it: This person has clearly demonstrated academic dishonesty. Do you trust him or her to be commercially honest?
You're being charged a pile of money for the solution. Do you suppose the "tutor" could resist getting the same money for no additional work by selling the same thing again?
Big. That is, we in the Department of Computer Science can't specify a penalty, because that is beyond our privileges. But we can tell you for sure that buying your work -- whether from a private tutor or from an "essay service" or from a freelance programmer -- is viewed as a very serious offence by the University. We've seen some heavy penalties.
We remove the advertisements for tutors we know are going to cause you trouble. But we can't be sure that everyone who advertises will behave responsibly.
It's up to you to ensure that the help you get from a private tutor is acceptable under the Code of Behaviour on Academic Matters.