Well with that subtle opening gambit you should be a master at this noble sport!
If you go to your boss and say
"Hi Boss, can I go out on the pish and will you pay for it?"
The answer is normally a resounding "eff orrf!" followed by a threat that if you are late for work the next day you will be fired. If you say that there is a boring networking event with target clients attending then he should say yes - just be prepared to collect business cards from everyone you meet.
Networking is exactly what is says: you are working at increasing the size of your network (pedants please don't point out that it should be called workingnet). Personal networks are the most cost-effective and effective ways of getting business. Simple. People like to do business with friends.
Is it a scam to get drunk and get the boss to pay? If you do it badly then yes. Done properly it is a fantastic way of making sure that wherever you go in the world you will have people who "know people" on whom you can call. This can save you money (getting advice on cheaper hotels and bars, etc) and makes getting business easier. It also may allow you to meet people who at some stage you may want to employ, or may want to work for (and they might want you to work for them).
I go to at least two "networking" events a week. I have over 1,000 contacts on my mobile phone for people in 16 countries. I eat out at company expense 4 nights a week (and have a reason if pressed by an auditor).
So in summary: if you can network, then do it. It increases your circle of friends and people you can call if you need something that your company or normal circle of confidants cannot supply.
A word of caution though: do not get bat-faced at these events, otherwise instead of the people in your local pub knowing you are a cnut when drunk(and who have known you for x number of years), you will let the business leaders of 100+ companies know that you are a nightmare. Not so good if you want a different job at any stage, and also bad as it will reflect very badly on the company you work for.
Where can you do it? (forgot to answer that part of the question). Almost anywhere. Approach local chambers of commerce, community events, local embassies and trade organisations. Golf clubs and private clubs are also great places.
Top tip though: do not come over as pushy. When networking listen more than talk, and do not prattle on about what you do or want to do unless the listener makes it clear that they want to listen to you. As you leave to say hello to other people leave with a "Very pleasant to chat to you, do you mind if I give you a call next week/tomorrow/whenever?" Works for me.