This is largely a career based trial and error, IMO. I suspect it changes radically over time, and changes with career field. My general take is that search engines are sophisticated enough that "Hello World" and "Hello-World" and even "hello world" will read as the same thing, besides, it would throw readers for a loop to see all three things spelled out separately In that case, pick the most common format you've seen.
They also seem to be acronym compliant most of the time. Mileage will vary of course, and be ware of very overloaded jargon. A good test is to feed your acronym into Google and see what comes up - if the first page or two is 90% the topic you meant - you're good, it's pretty common. But if the first few hits are for wildly divergent topics, figure that the acronym is muddy and spell it out, putting the acronym in parens.
Speaking purely to the computer world - the automated searches I've seen (and this is just conjecture -- I don't do this for a living) have been centered around technologies not practices. So "Java", not "object oriented". And the more specific the better - "Swing", "Hibernate" and "Struts" are going to produce closer matches and more interest than JEE. Think of terms like OOP as something so general you may be saying "computer science" at this point.
Here's my process for tuning for what I want:
1 - make an attempt to be honest and accurate in my resume/profile. Enunciate the cornucopia of hitwords for those areas were I am most keen to continue working.
2 - post, collect responses.
3 - periodically - I did this weekly/biweekly - review the cross section of responses from all sources. Do they slant in a way that you don't like? Review the resume and update accordingly. For example, I had so many softare web development hitwords that it didn't come through that a management role was table stakes for me. So I updated with many more words relating to managment, certification, policy and project management to redirect the search critieria, and whittled down the JEE stuff.
Rinse and repeat.
One of the nicest things about the job search these days is that you can rebroadcast your resume really easily on most sites, and a new update seems to trigger the search engines for a re-scan. So it can be a bit like back-ward engineering the engines - think of your resume as a net, and job hits as fish. When you don't like the fish, change the shape of your net. :)
