I know that this is common for most of you, but I just haven't done this before.

I have a United award ticket; first leg is on LH from EDI to FRA on ticket from United. I connect in FRA to a UA flight to IAD., and than UA onward to ROC.

I assume that I check in with LH in EDI and probably just hit a transfer desk in FRA. Any special tricks or procedures that I should know about

Yes you'll check in with LH in EDI and they'll probably give you your boarding passes for the UA flight, in which case you won't need to go to the transfer desk.

You might need to answer some security questions that US airlines are required to ask, but you can probably do it with the gate agent.

Paid / Award you always check in / chack bags with the operator of the first flight.

They should provide you with the connecting flights BP(s) (and LH will) but some may not (4U for one).

If it is contract agents in EDI (and I assume it will be), you may only receive the boarding pass EDI-FRA and you then need to go to the transfer desk. They will check your luggage to ROC, although you will need to collect your luggage in IAD to clear customs and then you will put it on the recheck luggage conveyor belt once you get through IAD customs.

The issue of the boarding pass confuses me as most of the time in non-LH and non-UA hubs they will only issue me the boarding pass for the first leg and tell me to go to the transfer desk at the next destination, but I will travel with friends who may or may not be on my reservation and they always receive all their boarding passes (I have 1K status and they do not).

So be prepared either way for the boarding pass issue. Luggage will get tagged to your final destination.

The US mandated asinine security questions will probably not be asked at EDI but more likely at FRA

I fly regularly from the UK to the US via FRA - lately I get the pleasure of answering the questions in both places.... The back of my passport looks like a 90 year old globe-trotter with all the stupid stickers....

More to the point, even if the US security questions were asked in EDI, FRA will most definitely ask again. At FRA there seem to be only two cases: if you do landside checkin at FRA, they ask, and stamp your boarding pass; if you don't have that local stamp, no matter how you got to the gate at FRA, you are shuttled aside for the questions.

Thank you all; it does not sound like it will a problem at all.

And I'm thinking that coming in will be easier since I'm going EWR to FRA on UA and then from FRA to ABZ on LH. My luggage should go all the way to ABZ without me having to pick it up in FRA on the way out correct?

Weird routing because I'm able to book BusinessFirst saver seats

Yes luggage will go through without issue - enjoy the FRA customs / security "maze" - believe me your luggage has it easier than you will....

I recently had a very similar situation, except my origin city was different.

In addition to the the previous replies, I will add that LH recommends you do online check-in prior to departure. This process took me about 20 minutes for the two of us, much longer and more tedious than OLCI with UA. I would encourage you to do this as it may expedite things at your origin airport; it certainly did for me.

Do they recommend OCLI even though the other flights, on the same ticket, are on UA?

If you are signed up for Precheck you might consider exchanging the LH BPs for UA BPs in FRA. When flying back to the US, my LH BPs never have Precheck and getting the new BPs in FRA saves me from having to reprint them in the US. Of course this depends where you are making your INTL-DOM connect, IAD in your case which might not make a difference.

Your luggage will go straight to ABZ, and you'll pick it up in the luggage shed outside the airport.

This is a ProTip, but only makes a difference if you go through the regular security to get to your domestic connection in the US, e.g., if you are landing at TBIT at LAX and then walking to T7 to catch a UA flight. I have never been through a dedicated post-immigration security station that had PreCheck. While you are landslide, you can also just hit a carry-on only kiosk to get the UA BP.