Flights to New Zealand usually land in Auckland, the nation's largest metropolis that is located on the North Island of the country. Auckland International Airport is quite arguably the country's busiest airport. There are flights to New Zealand from most major airports all over Europe and the rest of the world. A flight from the United Kingdom can take from twenty two to twenty four hours to reach the Auckland International Airport in New Zealand.
A concrete plan of what you are going to do is of utmost importance. Once you've selected your purpose of visit you must apply for the appropriate visa. You need a working holiday visa if you are visiting for temporary business related purposes, a residency permit if you plan on settling there, a work permit if you intend to do visit and do business there on a relatively permanent basis, a visitor visa if you're just passing through and so on.
Your visa must be valid for at least six months longer than you plan to stay to be on the safe side of the law.
People with visitors' visas to New Zealand must have a return ticket, an onward flight or proof of funds to prove they can buy the same on reaching New Zealand. People with work permits and working holiday visas will be allowed entry on a one way flight only if they have proof of funds that will allow them to support themselves during the stay as well as buy an outward ticket. The outward ticket in addition must be to a country they are allowed entry into.
People from Visa Waiver countries (such as Argentina, Brazil, Austria, Belgium, France etc) may only enter the country when they have outward flight tickets or official confirmation that one is booked and paid for in their name.
Citizens and permanent residents of Australia and New Zealand can enter the country with a one-way ticket only if have a valid passport or returning resident's visa on their foreign passport for Australia or New Zealand. Entry into the country will be restricted if one does not comply with these rules.
Only after these conditions are verified is it safe to look at flight companies, peruse schedules and buy plane tickets. Unscrupulous travel agents may cunningly sell you a one-way ticket while knowing that you might not be allowed entry into the country on reaching the border. Be on the alert for any foul play while making all transactions. In case you do have a twelve-month working permit and intend to be in the country the entire duration flight schedules will not be available so much in advance and you will have to make careful and cautious arrangements.
The safest thing to do is do your own research regarding regulations (you can visit New Zealand's immigration website), visit various travel agents, get quotations and compare them to find the perfect price for your budget. You can also visit online websites to search for the appropriate flight, book it and then pay for it with a credit card. A well-worded google search will aid your work to such an end.
Traveling to New Zealand without an onward ticket can be an expensive mistake, as you will not be allowed on the flight.