Here's what I can tell you.A visitor's visa is the easiest,and it's free if it's up to three months,but it doesn't allow you to work and cash in hand is quite a dream.
Skilled migration,which means,how many points can you get and such,has to be done from his/her own country and requires more than an year processing,and remember,nothing is guaranteed and the thousands of dollars you spend on it(4 thousand australian or round there,if you include the fees for the immigration lawyer),is in no way refundable.
A student visa allows you to stay and work in the country for schooling purposes,and you're allowed to work up to 20 hours a week.Once you take taxation off,you can barely pay rent and I wouldn't advise it.
a working visa allows you to work for holyday purposes up to 12 months,provided a curriculum vitae,a letter and a bank statement showing you have a minimum of 7 000 au$ savings to support yourself.By law You are not allowed to work for more than three months each employer and that gives you a pretty hard time.I nearly forgot,you have to be under 25.
Marrying someone is better if processed in her/his own country.It costs around 2000 au$,between taxations and various examinations.More if done in Australia. First they have to get married,then provide documents,letters from witnesses,correspondence,love letters,joined bank accounts statements,joined bills and things,then they wait for a certain amount of months and remember,in those months he/she won't be allowed to work.Then the Immigration office might allow the spouse to be a temporary resident(no social security,medical assistance or rights at all) in Oz for two to five years.Then she/he'll be given permanent residence,provided documentation that the couple is still loving and happy and such.
an altrnative to marriage is de facto relationship migration,but he/she'll have to convive together for 12 months before claiming it.
There are many other categories.i'm going to the bloody immigration office this thursday so if you have any question I might forward to the immigration monsters,let me know.