Biggest expatriate challenges?

Limit your contact with other expats. Other expats are easy to get to know and befriend, but you can quickly find yourself trapped in the expat bubble if they are your only social outlet and as I said, most only stay a few years, so if you're in for the long haul, you'll find yourself waving goodbye to a lot of people. Instead try to socialize with locals - a very difficult nut to crack, but once cracked it expands rapidly as you'll branch out through one to their friends, the friends of their friends and so on.

The other advantage of befriending locals is that you learn the 'tricks' of negotiating life in any country; getting things cheaper, your rights as a consumer or tenant, places to go and so on. If you are stuck in the expat bubble, you will never learn any of these.

As a caveat, having a trailing spouse or partner can present an obstacle to this. It's all too easy not to bother making new friends because you're ultimately not alone. You need to overcome this. Also, I only suggest limiting with contact expats, not avoiding them altogether.

Seek the cultural commonalities and use that as a starting point. While you'll get an element of culture shock everywhere, there's always going to be parts of the culture you can identify with. For example, the Swiss are historically an agrarian people and to this day many, even in the cities, are essentially one or two generations away from some farming village with a tiny population, where naturally if you can't say something good about someone, you'll say nothing, you'll always be polite and where deals are inevitably done over a few beers, leading to a strong passive aggressive mindset.

Sound familiar? Yup, your average Irishman. Where it begins to differ, is that they'll be far more organized, punctual and methodical. So once you've got into your head the simple generalization that a Swiss is like an Irishman with Asperger Syndrome, it makes it a lot easier to relate to them.

Learn the language. Should be obvious, but it's very easy in many countries to get by on English and before you know it you'll have been living there and still only have enough to order a meal at a restaurant. Here, as has been said, language is a complex thing. Other than having four official languages - German, French, Italian and Rumantsch (the Swiss equivalent of Irish) - dialects play a big part (most Swiss Germans can't even understand some of the more extreme dialects, such as Walisdeutsch).

Again, socializing with locals goes a long way in this regard (chatting up the opposite sex is an excellent way to focus the mind). The approach I took was in stages; starting with High (standard) German, then slowly replacing German words with Swiss ones and finally adopting the grammar (or lack thereof). Different countries will present different challenges where it comes to language though.

Other countries have seasons. Oddly, this is something you can easily overlook, but Ireland has a pretty mild (bordering to boring) climate which rarely goes too far beyond zero and 20 degrees. This is not the case in many other places where here, even in the Voralpen can easily go from over 30 degrees in the Summer to under minus 15 in the winter. What this means is you need to take a little more care, especially if there's a snap weather change; I had a nasty cold or flu every year for the first three I was here, until I got used to this.