A key factor would be the European Central Bank interest rate. The higher the interest rate, the more that lenders of the currency are paid by borrowers, so owning more EUR enables a bank to lend more.
GDP and GDP growth within the Eurozone is also important, especially Germany's. Also inflation, unemployment, balance of trade (imports:exports) etc. etc. Follow an economic calendar such as at DailyFX.com for key announcements, news and their significance. But do not assume its easy to trade these factors short-term, its about the hardest thing you could try.