All methods are very effective. Wiring money is fast, but it is also quite expensive. Your local bank can provide complete details on all three methods. If, for example, you are going to study in Germany but decide to enter via a train from Austria, take a bit of each currency to cover train rides and taxis. If possible, try to get some coins for vending machines, phone calls, or for making change.
Some students take most of their money in traveler's checks.
Most brands are readily accepted, especially in major population centers. When cashing traveler's checks overseas, banks generally offer a better rate of exchange than tourist bureaus, train stations, hotels, or a variety of entrepreneurial black marketeers. It is worth checking out several banks for the best exchange rates and transaction fees. In some countries you may be able to take care of these transactions at post offices. Make a budget for your stay.