1. Compare before you buy. The most sensible thing to do is to compare the exchange rates provided by the different vendors and choose the best one for yourself.
2. Consolidate your transactions. Every currency exchange has its associated costs, sometimes by consolidating several transactions, you may save money and the foreign exchange provider may even offer you better rates.
3. Check before you travel. Depending on your intended destination, you may have issues exchanging for local currencies outside of the country, especially if you're travelling to a country whose currency is less used.
4. Look for a buy-back guarantee. Some currency exchange companies allow you to lock in the exchange rate you bought at without any commission fees.
5. Don't leave it until the last minute. Sorting out your currency should be a vital part of your trip preparations.
6. Beware of counterfeits. Every country has its fair share of counterfeit currency, take note of the watermarks and other security features to spot the fake currencies.