Ireland border crossings

As for crossing from the North into the Republic and vice versa, nothing. There are no border formlities, nobody to check documents, and you don't even have to stop but just drive through. You don't even realise you have crossed until you see different road signs, distances given in miles (in the North) and km (in the Republic) and different road numbering. If you are driving a hired car, just check with the rental staff it's ok to cross the border. Most will be ok, provided you return the car on the same side.

"What is entailed if driving into Northern Ireland from the area of Castleblayney (or County Cavan area)? Any suggestions, recommendations, advice?"

That's a very strange question. What do you think will be entailed other than taking the correct road?

It's a fair question, it wasn't so long ago that crossing the border potentially entailed a lot. As #1 says though that's not the case any more, assuming that OP doesn't require a visa to enter either jurisdiction (and I'm guessing she doesn't).

I guess if you look at a map it is a question to be asked; it is a unique (possibly) crossing between countries in that there are different laws and currencies on either side but no border control.

How else will you notice? Going over into Newry a few years back the buildings on the border are quite well protected (lots of window grates and steel shutters) and there are was tower (but I think all these are gone now).

This is a google search for Corran, Country Cavan but I am not sure what is there (and the satellite imagery doesn't look promising.

Can you help a bit on the memoir thing? I know you say it was written in 1910 but some farms and some small villages were abdandoned in the second half of the 18th century and is it possible this was one of them?

Methinks you need to improve your search skills. All the following info comes from Google.ie

Searching for "Methodist Church Arva" throws up a load of results for Arva (also spelled Arvagh and possibly at one time Ava). The local news frequently mentions the Methodist Church at Corlisbratten, which seems to be in Arva. If your family were Methodist, they probably frequented this church, in which case there may well be records there. There aren't all that many Methodist churches in Ireland (most Protestants would be Church of Ireland) but if there was another church, the people at the existing church should know and might even have the records.

Searching for Corrinairy House throws up a some historical records referring to Corrinairy Lodge, Co Cavan. This is maybe the same place.

The Wikipediea entry for Arvagh mentions a census of 1815, which means that census data exists, probably for other dates, and should be available online for a fee.

Search for "corran arva cavan" brings up a lot of records, including one mentioning a family living at Corran.

good luck.

Sorry and further there is this: FYFE and MORTON - On the 24th ult., in Derry-lane Church, by the Rev. J. J. EGAN, Margaret Jane, youngest daughter of the late Mr. JOHNSTON MORTON, Corran Cottage, to Mr. George Fyfe, Lake View Lodge, Arva from an 1877 newspaper.

I assume the OP is North American and thinking of the US Canada border.
Don't. Internal borders in the EU have mostly been abolished. Unlike #4's recollections, you can drive from Sweden to Portugal - or, indeed, from Armagh to Castleblaney - without being made aware of one.

The only borders of note are between the EU and Russia, Turkey etc. and some Balkan states. And the maritime/air border between fortress England and its continental neighbours, supposedly vital for wars on terror/drugs etc. but more to do with anti European sentiment in the UK population.

#7 you can still notice where the badlands were (the old RUC station was still there two year's ago) and you can still spot the move if you look for this kind of thing as you go along the A1. But yeah, it is possible not to be aware. Not quite sure where Sweden to Portugal comes into it.

And the anti-Euro sentiment thing, I am not sure about. Particularly since it is easy, and deliberately so, to enter UK from Europe without presenting a passport to enter UK. And all European countries require you to present passport going into their country so I am not sure why they do it except for security.