There are lots of ways; most importantly you need up-to-date information on exchange rates and fees. When you use BestExchangeRates you can see clearly which currency vendor is offering the best deal for your needs, most importantly who is taking the smallest margin and fees to give you the largest possible converted amount.
Below is an example of the AUDGBP percentage margins that are charged by banks and non-bank currency providers. For transfers you should avoid paying a margin any where above 1.5 per cent for major currencies (USD, EUR, AUD, GBP, CAD, NZD, CHF etc) and 3 per cent for minors (CNY, BRL etc). When buying Travel Money and loading travel cards the margins tend to be larger starting at around 4% for the majors.
You might also consider using a non-bank currency provider such as a Foreign exchange broker. These brokers deal directly with the currency markets which means they can offer highly competitive exchange rates on all major currencies, they can better the rates offered by banks by 3% and often even more – for a $10,000 transfer you would save $300. They can also offer you advice on timing your transaction and also provide in-depth research and online tools so that you obtain the best possible exchange rate. Opening an account with the Foreign exchange brokers is quick, simple and completely free.
See this experiment comparing $100K sent with a non-bank currency provider (OzForex) and $100K sent via a Bank.