So what should I do if I want to see Rafa in his, say, 2nd round match? Do you have any tipps for me, please?
At the USO, with the exception of the first round, it's actually possible to make an educated guess as to which day (not session) the top two seeds will play on, unless the schedule has been affected by inclimate weather. Unless they have changed it, they usually play the top half of the draw the day before the bottom half. Assuming that Nadal will still be ranked #2 by the time seeds are made (obviously not set in stone, but IMO he'll still be #2, although it will be very close), he'll play on the second day of the men's round 2, which according to the USO website is Friday (http://www.usopen.org/schedules/default.sps
). This is when Nadal played last year too (but not in 2006--this is not set in stone).
However, even if you can make a good guess as to what day he'll play, you won't know whether it'll be during the day or night session, since he'll probably play in Arthur Ashe, which requires a special ticket that grants you access during either the day or night, but not both (although you could buy tickets for both). This is really a toss-up. One of the two night matches will be a WTA match (that is for certain). They like to put the players with the biggest (American) star power in the night session, so they can maximize primetime American TV viewership. Furthermore, European players playing during the day will maximize European TV viewership. However, Nadal is pretty big in the US and in the past organizers have not hesitated to put him on during the night session. IMO the only male players who will trump Nadal for a space in the night session are Roddick, Federer (who if he is still #1 will be in the top half), and probably Blake. So, if either Roddick or Blake is in the bottom half of the draw, there is a decent chance that Nadal will play during the day.
So, this probably isn't a huge help, but if I were you I would get a daytime AA ticket for Friday (especially since you'll still be able to access the outer courts during the day, whereas an evening AA ticket will not grant you grounds access during the day). However, before you buy you should know that there is a good chance that he may not play during that session. Organizers don't always follow this logic and like to mix it up to give all the top players the good times/courts (i.e. Roddick played a day match on AA during R2 last year while Blake had the night spot, even though Roddick is obviously a much bigger star). Nadal didn't even play during the Friday day session last year or in 2006, despite perfect weather last year. Don't be disappointed if it doesn't work out, especially since there is a good chance that it won't.
I know this wasn't a big help, but hopefully I at least provided some insight into the scheduling process. To summarize, there really isn't a reliable way to figure it out.