I usually look over the tags for c++ and java, but they are all usually answered within a couple of seconds. How can I gain some reputation? I was hoping to get into the chat rooms sometime this year.
Another way to get a reputation boost would be to leverage the account association bonus.
There are many other Stack Exchange sites dealing with varying topics. Perhaps you'll be able to answer a few questions on one of those sites and once you reach 200 reputation there, you can associate your Stack Overflow account and receive a 100 reputation bonus.
Take a look at some of the sites, you might find it much easier on a different site to get that initial reputation.
Just to play devil's advocate for a moment, Lix's answer holds a beautiful vision of what SO should be and is definitely not the fastest way to get the 20 rep required for chat.
The fastest way to get 20 rep quickly is to give an answer that's first, correct, and seen. Having your answer be seen is the most important. You could be writing Shakespeare in response to an e107 question and it wouldn't matter because no one would see it. No views = no upvotes. The best way to be seen to is answer easy questions in popular tags. Everyone looks at the easy looking questions; everyone follows popular tags. Being first is another part of being seen. Everyone sees the first answer; if it's reasonable, it'll get upvotes. Being correct is a distant third. If you give the first answer to an easy question in a popular tag, you'll get upvotes as long as your answer isn't outright wrong. So make sure that websockets are working to see questions as they come up, and when an easy looking one in a good tag comes up, get in there fast and say something that's not wrong. Your answer won't be the best, and it probably won't be accepted, but it'll get you a couple upvotes.
Allow me to expand on @bart's comment...
I frequent the php and jquery tags. These tags are similar to the c++ tag in that they have a high volume not only of questions, but answers too. Many times there will by multiple answers to a post within seconds of it being posted. Usually these lightning fast answers are one liners and don't give much explanation and while they might technically answer the question they provide no additional information or explanations as to why the problem exists in the first place. These answers will probably get an upvote or two (just for being correct). I really don't like these types of answers because I feel that they are suggesting to the OP to just copy and paste their code and it will fix the issue. I do not believe that is what Stack Overflow is about or how it should work.
The idea here is to create a database of questions and answers that will be able to help not only the person asking the question, but also people in the future who are experiencing the same or similar problems. Future visitors will most likely have similar (but not identical) code making these short code only or one liner answers pretty useless. It is always preferable to add some information and explanations (where possible) to a post to ensure that the OP and future visitors will understand the problem and the solution.
Basically, what I'm trying to convey in my rant is that people who put the effort into their answers will ultimately benefit in the long run by providing complete and concise answers including examples, explanations and possibly the thought process of the person answering. These posts will definitely take longer to type up and there will most likely be a few answers already posted (and they'll probably already have some upvotes too). Don't let this deter you from posting your own fantastic answer. Take the time, put in the effort and don't worry too much about gaining reputation. Reputation is a by-product of contributing great material to the site. The OP will appreciate your explanations and in the event of multiple correct answers, they might choose the most comprehensive answer to mark as the accepted one as opposed to the quickest (this is not always the case... but lets try to stay optimistic OK? ;)
Looking at your reputation (before I submit this answer) I see that you already have reached the required 20 rep to get into chat...so I guess...problem solved :P