This is tricky for sure.
It all depends on were you live. I tryed to contact one member that I saw was living in Sweden when I started up.
There was not many Swedes around at that time that hang out on forums back then.
So I decided to PM this guy and try to see what he was like. We did this back and forth some before I gave him my number.
He called me up and we decided to meet. We did, and from that moment on he has become a really close friend of mine.
This is just one way. I have also talked to toystores and try to see if there is other adults that buys alot of LEGO
and if they talk about there hobby when they are there.
Then there always is the LUG´s or big conventions that is really good to get contact with others.
Attend at different events is another good thing as well, were I also met several persons.
Those are the ways I have done so far and today I have several friends that I talk to daily, weekly or monthly.
I see several of them a few times per year and some even more often.
Hope this helps you some.