Here's how I met mine (to bore you all but I suppose also to confirm the "common grounds")

When I was dumped back in 2008 2 colleagues at the bank and a customer (we are all roughly the same age) were going through the same thing.

We laughed, cried, drank - drank some more and basically helped each oother through it. One of them moved in with me and for that short period of time we were each others support.

It's funny because we now always say we were meant to meet up and help each other through that time.

My 4th 'bessie' is also my sis in law (married to hubbys brother). Our common bond is that fact that the oldest sister of our two guys hates the both of us hahahahaha

I'm only now starting to make more friends outside of the ex-pat circle.
I'm sure most people who move here struggle to make friends outside their own 'kind', hence ethnic groupings in the inner cities.
It's tougher than in the UK where the people you work with also form part of your social circle. That doesn't seem to happen here.

I think it does but it depends on the culture of the workplace and one's willingness to participate in post-work activities. It's easier for me when the post-work activity is drinking, less so when it's going to church or jogging.

A problem with our business is that everyone's geographically dispersed. We went to a birthday party on the weekend, for someone I once worked with who's remained a friend. I knew a fair number of the people there from parties at his house, from fishing trips and the like. The problem being that they all live in or around Washington DC so getting there involves two days of driving or an expensive flight.

Giving the increasing trend to virtual teams and working from home, work derived social events will, I think, more and more often start with a email "I'm changing planes near you, got time for a beer?". The internet also has a role, in my era of flying around all the time I'd post on a talkboard "stuck in ABC for a day, anyone up for a beer?" and met a vast number of people that way. Several have remained friends but someone in, say, Amsterdam, isn't the kind of friend one can call for emergency babysitting.

Another way to make friends is though organisations like meetup.com.

When I was in the UK learning french I would go to a weekly meetup to practice.

They are often held in bars and cofee shops.

Though friends ask alot they are also willing to give alot. One loaned my wife his mercerdes to practice on while she was learning to drive, another spoke to one of his golfing buddies to get me my current job.

There are not that many british expats where I am and yes they do love the way we talk, but without these friends we would have been totally lost.

How did we make them? Some of them offered to help when we moved into the neighbourhood and we took them up on their offer to show us around, tell us where all the bargains were to be had, and who the best dentist was.

Some were made through our children. Before I will let my child stay over at someones house, I have to get to know their parents pretty well. Others were made on camping trips (Winter camp is a very bonding experience).