Flights from EWR to FRA or MUC

Munich is considered one of the best airports in the world for making connections. I find Frankfurt to be nightmare in that respect. I also use Untied miles for Lufthansa codes shares out of Newark, no major issues. Although Lufthansa uses termimal B at EWR which is not as nice as United's terminal C:(

For complicated itineraries using points, it could be best to phone United and talk to an agent in the awards program. Be alert to the possibility that a multi-city route may cost a lot more points.
I note that Austrian and United are members of Star Alliance so your points might be valid with Austrian. It flies non-stop from Newark to Vienna, and non-stops are always my first choice. Again, a real live United agent may be your easiest source of info.
It's never too early to book awards travel. Then cross your fingers that routes or times don't change.

United's website makes it very easy to redeem miles for United and codeshare flights; I never had to telephone them. Unless you're flying to London or Paris, it's rare that one is able to use miles on non-stop flights, I've always had to connect somewhere in Germany via Lufthansa. Lufthansa uses larger planes across the Atlantic compared to United's narrow body 757s so they have more capacity.

If not using points, anyone have any ideas if it's too early too book in that case?

As long as you stay with Star Alliance airlines (United, Lufthansa, Austrian Air), Munich will be more convenient. Their trans-Atlantic flights come into Terminal 2 and their flights to Vienna leave from Terminal 2. OTOH, some other airlines, Niki, for example, use Terminal 1 for it's flight to Vienna. The Terminal are a considerable distance apart.

We are in your same situation except we're flying into Ljubljana and out of Dubrovnik. We've been tracking the flights for a couple of months on Yapta and they've varied by less than $100. We travelled in Sept 2013 and booked almost 7 months in advance and the price never went down but prices seem to be a bit higher this year. On the other hand, we dislike making reservations so far in advance lest our plans have to change. It's a tough call.

Regarding points, are you using the points or accumulating them? To use points just check award travel at the bottom of United reservation screen and you can then select the available flights and class you want.

Thanks Carol! I'm not sure yet on how I'm using the points but I have used the United check off box. I'm seeing the same thing on the price variation, not much. Our plans are pretty much fixed so I guess it's a roll of the dice. Good luck on your trip!

Have you considered the direct flight on Austrian? Austrian is also star alliance.

Enyland, we have used United points to get to Italy a few times via Frankfurt. Never from EWR however. All from the west coast via ORD or Dulles. My point here is that if you are flying into one airport and returning via another (multi-city), I have never been able to do this online. True, you can make multi-city selections when you are not using points but when you switch to points only, the multi-city option doesn't seem to be there. I've had to call each time. No problems. United has always been very helpful. Also, I call 333 days before the time of travel which is when the flights first appear. Seats reserved for points are not numerous.

"....True, you can make multi-city selections when you are not
using points but when you switch to points only, the multi-city option
doesn't seem to be there...."

One absolutely can redeem miles for open-jaw itineraries via Untied's (formerly Continental's) website. I've done it about ten times, each one was multi-city. Are you possibly referring to United's old reservation system before the merger?

Thank you everyone!