There is a pattern to big international competitions and, to a lesser degree, this pattern is also evident in big club competitions such as the Champions League. The pattern is very simply this:
They start in a cautious, cagey way with teams finding their feet and testing the opposition, they very quickly move on to very positive and aggressive play as teams find themselves in need of points or buoyed by a good start with the knowledge now that they can qualify to the next stage with a good performance. And finally they go back to the cautious play.
If you want a timeline for that then, typically, it would be:
Very cautious first game, ramped up second and third (group stages) when trying to get the to the 2nd round. Cautious and testing quarter finals and semi-finals whilst trying not to make mistakes against what is clearly good competition and the high octane release (and relief) of finals and play-offs having realised that it was all for this.
That is a simple summary of course with obvious and notable exceptions (Germany v Brazil, World Cup 2014 semi-finals) but when I look back at and think back on past international competitions that would be how I would describe the evolving process in the majority of these competitions. The most consistent of those patterns generally appears to be in the very first game that a team plays and it seems logical that this would be the case.
No-one wants to make mistakes in their opening game. Too many teams have underestimated a seemingly underpowered underdog only to find that their raw enthusiasm for the event has turned them into super-heroes. Once the measure of a team has been taken, as evidenced by the results in the first games, then the real games commence and nowhere is the exposed, unprepared team more revealed than in the second game of a big competition (as evidenced by Spain against Chile in World Cup 2014 for example).
So here’s my big tip:
Be cautious yourself in the first games played at the Euros and look to make your first big killing blows in games 2 and 3. Game 3 is always a more obvious game to assess. Can they qualify? Can they fail to qualify? Is there an incentive for them. That’s all you really need to know.