Expectations

Tutorials

For tutorials there is usually the expectation that a tutor will prepare for the class, deliver the class, and have marking outside the class time. Tutors' pay is packaged in a way that reflects that: so for one class you get paid for 3 hours work (preparation, delivery, marking).
 
There are a few points to note though. The first is that if you're taking other tutorial groups in the same subject, it is deemed that you don't need to prepare the same material twice. Hence for each subsequent tutorial group (called 'repeat tutorials') you get paid for 2 hours work (delivery, marking).
 
The second point to note is what is meant by 'preparation'. Some teaching areas might interpret preparation as attending the lecture. Others might want you to read that week's articles or solve the exercises. Another area might simply expect you'll spend the time preparing the structure of the class from a teaching perspective: how much time you'll spend on group discussion, how you'll deal with that awkward student, etc. The point is it's pretty much up to an area to determine what you are to do for that hour of 'preparation'.
 
The third point to note is marking. The marking associated with each tutorial can accumulate. That is, there will be some weeks in which you have no marking at all, but get paid for it. In other weeks you'll have many more hours of marking than the number of classes you have.
 
Where an area recognises that over the semester they expect you'll have more hours of marking than the packaged system pays you, they will include an appropriate number of hours of additional marking to your contract.
 

Laboratories

Lab demonstrators are typically not required to prepare before their lab or to mark student work outside the lab time (if they are, they must be paid for it). So generally, if you take a 3 hour lab, you will be paid for 3 hours.
 

Consultation with students outside of class

Part of the role of a tutor is to be reasonably available to consult with students outside of class if they have any questions or concerns about assignments, what they have learned in tutorials, etc.. So you may be expected to keep set consultation hours aside for consulting with your students outside of class (usually 1hr per week per tutorial/laboratory).