Ok -- so how do you do it.
#1 -- showing up is half the battle --- or so it is said. If you don't participate, you don't network. Having a membership card and getting a newsletter is not sufficient. Within the IEEE Computer Society, there are many places you can show up:
#2 - Introduce your self to a few folks at the events
Until you know a name or two, and have a few folks who know your name, you don't have any network links.
Business cards are invaluable for swapping contact & name information - With online sources like VistaPrint, getting your own is cheap.
There are seminars on "three minute networking" -- parallel to the "three minute date" -- that teach you to articulate your "business" in a few sentences so you can "work a room", connecting with folks that may have common interests. -- this approach makes sense for sales persons (sorting out prospects), politicians, and such. Your best bet is to try to make sure you say a thing or two, contribute from your own perspective, so folks have a sense for who you are. And listen to the perspectives of others. Then during a break, touch base with the folks who seem to have common interests ... "gee, I thought your comment on how useless ram jet peanut butter spreaders were was right on target." -- folks call it "small talk" --- "who do you work for? ... what do you do for Acme? " - if you listen to these answers carefully, you can identify where additional questions might be appropriate "do you use Java" or "DSP's" or ... even repeating the job title back to the person as a question, inviting them to expand on what it might mean. --- some percentage of these connections will not appear to have high value, others will clearly reflect strong areas of common interest. --- I say "appear to have high value", but I note that much of the highest impact innovation occurs when folks span beyond their own field and gain a perspective from something a bit different. Velcro being inspired by seeds with nasty hooks that caught in a dog's fur; the spreadsheet being inspired by a discussion between a finance guy and a computer guy, etc. So you may not want to presume that a contact is implicitly a dead end -- but some will be. -- The good news is this is not like asking someone for a date -- failure to follow up is not earth-shattering, just a practical question of pursuing common interests.
#3 - stay in touch.
Attend the next meeting of the group, and say hello (by name ... it is useful to learn names; or just admit it... I'm afraid I've forgotten your name... and let the person inform you -- take the time to write it down this time!) I like to put notes on the back of business cards (which is not polite in some Asian cultures) indicating where and when I met someone, and points to follow up on, or common interests. Then I can go back to that stack of cards and identify the email address for "that lady who headed up the institute on ..."; depending on how "natural' all of this is for you, you may want to take some time when you get back home to write up notes, annotate your email list entries, or an online database of contacts. (Sales folks do this all the time; but don't let that discourage you -- your ability to draw on these resources in the future is invaluable, and folks will appreciate the fact that you make the effort to recall who they are and their interests.)
You may want to follow up on in-person interactions with questions or notes on common things over time. When I trip into an article or announcement, or pointer that I associate with one of my contacts, I will email it their way. I try to avoid too many of these with any one person (I don't want to be a pest) ... but a few times a year it makes sense.
#4 - use your contacts appropriately
Part of this is staying in touch. But, invite them to events of common interest ('did you see this meeting?'), ask them for insight or opinions on things where they have knowledge. There are points in time where you will need contacts ... you lose your job, are trying to locate the best training program, figure out how to connect some program into a database, get a good reference on a new technology. Some of these things can be accomplished by "going to the web" ... but when you do that you lose the personal connection, and the acknowledgment that this contact you know may have some good answers. Of course, hopefully folks will use you as well -- try to be helpful, and avoid being dismissive.