Hello and welcome to LessWrong!
You will certainly meet some interesting folk here. The best way to start would be to head on over to the Discussion board. That's where the day-to-day conversations of LW take place. It's also the best place to get a feel for the community's attitudes and standards. I'd definitely suggest lurking a bit. Then, you can observe the conversations of other LWers, and, when you're bursting to join in, add to the comments.
Another great place to start is on the latest Open Thread. Open Threads are places for casual conversations and questions, though that doesn't stop the conversations from developing into weighty discussions or intense debates. If you have anything you want to ask or say, it's a good place to start. It'll also give you practice if you want to one day create full fledged articles of your own.
If you're interested in diving into some of the literature here at LessWrong, you'll find the Sequences brought up again and again. These are a (LARGE) collection of posts, mostly by user Eliezer Yudkowsky, covering a variety of topics but centered around the art of rationality and related issues. Very helpful reading for the interested, but it can be a little overwhelming, when you're just joining. If you want a little taste of LessWrong literature, check out the linked articles on the About page or some friendly guides to the Sequences. (XiXiDu's and Benito's are often recommended). These can ease you into the literature and let you find the parts that most interest you, without overwhelming you with details, discussion, and references.
If Roko's Basilisk interested you, I'd suggest checking out the Yudkowsky paper, Coherent Extrapolated Volition, that the Business Insider article linked to, as well as the LW sequences on ethics and artificial intelligence.
Hope you'll be adding your own voice to the conversation soon!
A few notes about the site mechanics
A few notes about the community
If English is not your first language, don't let that make you afraid to post or comment. You can get English help on Discussion- or Main-level posts by sending a PM to one of the following users (use the "send message" link on the upper right of their user page). Either put the text of the post in the PM, or just say that you'd like English help and you'll get a response with an email address.
* Normal_Anomaly
* Randaly
* shokwave
* Barry Cotter
A note for theists: you will find the Less Wrong community to be predominantly atheist, though not completely so, and most of us are genuinely respectful of religious people who keep the usual community norms. It's worth saying that we might think religion is off-topic in some places where you think it's on-topic, so be thoughtful about where and how you start explicitly talking about it; some of us are happy to talk about religion, some of us aren't interested. Bear in mind that many of us really, truly have given full consideration to theistic claims and found them to be false, so starting with the most common arguments is pretty likely just to annoy people. Anyhow, it's absolutely OK to mention that you're religious in your welcome post and to invite a discussion there.
A list of some posts that are pretty awesome
I recommend the major sequences to everybody, but I realize how daunting they look at first. So for purposes of immediate gratification, the following posts are particularly interesting/illuminating/provocative and don't require any previous reading:
More suggestions are welcome! Or just check out the top-rated posts from the history of Less Wrong. Most posts at +50 or more are well worth your time.
Welcome to Less Wrong, and we look forward to hearing from you throughout the site!
Once a post gets over 500 comments, the site stops showing them all by default. If this post has 500 comments and you have 20 karma, please do start the next welcome post; a new post is a good perennial way to encourage newcomers and lurkers to introduce themselves. (Step-by-step, foolproof instructions here; takes <180seconds.)
If there's anything I should add or update on this post (especially broken links), please send me a private message—I may not notice a comment on the post.
Finally, a big thank you to everyone that helped write this post via its predecessors!