With credit to one of the more experienced members on the site, mxyzplk, I thought I'd ask where noobs like me should ask or find answers to basic questions about Dungeons & Dragons mechanics if we are having trouble interpreting the text in the Player's Handbook (PHB)/Dungeon Master's Guide (DMG)/Monster Manual (MM)? Please be more specific/explicit than just "your FLGS or the game SRD" as I don't necessarily know all the acronyms yet :)
When you're just getting started, it is certainly possible to figure out the game from the books and just start running it for your friends. That's how I and others learned to game "back in the day." But there are certainly things that can help.
Huh? If you are profoundly and existentially confused about "what is roleplaying", see What is role-playing, and where do I start? and if confused about the general nature of D&D see I'm at a loss with “Dungeons and Dragons.” How does one play it, anyway?
READ THE BOOK. The Player's Handbook (PHB), cover to cover. I know you said you've read it, but no really, read it. Especially with 4e D&D they really tried to write to a simpler grade level and have copious examples of anything trying. If you closely engage and read the book, many of those questions will go away (and you'll get less newbie haters when you subsequently go looking for help). Use normal lookups - a word you don't understand? If it's a game term look at the Glossary or index; if it's a normal English word check a dictionary. See also: Playing 4th Ed D&D for the first time, what should I read to avoid holding everyone back?
Join a game. This is going to be your #1 route to very, very quickly answering 200 possible basic questions because in one round of combat you'll see people doing all the dice addition, checks, etc. Check with your friends. See Where can I find other RPG players? For D&D, there's a D&D Encounters program where there are demos and games being run in most gaming stores on an ongoing basis. You can join in, or if you just want to watch, you can watch. There's meetups, conventions, any number of places where you can join or observe a real live game.
Watch a game. If you are having trouble in meatspace, consider watching one of the many video and/or audio podcasts of what is usually called "actual play." See Where can I find actual play podcasts for RPGs?, search on iTunes, etc. Or you can read play-by-post games, see Where can I find transcripts of actual game sessions?
Try the beginner box. If the full game is still too confusing, consider the D&D Starter Set (Red Box). It's fewer rules and more newbie-helpful guidance.
Seek help. Needless to say if you know anyone who's played an RPG they can explain it to you better (and I GUARAN-DAMN-TEE you know someone who's played D&D - it's been around since the '70's and have been popular over time, so a parent, a teacher, a friend, someone's done it - ASK AROUND). If you are a brain in a jar, then for super basic "I totally don't know how to do this" questions it's probably quickest to do it in RPG.SE chat. If you want someone to personally take you under their wing and show you the ropes, ask for help there or on a forum, like one of these.
Ask questions on RPG.SE. It's not that beginner questions aren't welcome here - there are just some questions so basic that it's much more efficient to have someone in person or chat talk you through "how to add 1d8 + 4" without clogging the site with hundreds of those questions - you'll get answers faster.
Note that as soon as you have played a game, further questions (like about the DMG or MM) can be asked here, that's not too basic, as long as you've read the book first).
Excuse me for answering my own question, but I thought I'd add a couple of resources that have been touched upon by other users in chat, comments, etc.
Learn by doing The easiest way to clear up basic misunderstandings or confusion regarding the rules is to play in or observe a game run by more experienced players. If you are unsuccessful in finding an active game in your area (please see #2), there are many online resources. For instance, youtube has recorded DnD sessions available (particularly funny examples include the the PAX celebrity games, such as "PAX Celebrity Game, Part 1" [YouTube]).
Try asking at your friendly local gaming store The people at these places are generally knowledgeable and eager to share their know-how. Moreover, they often organize/run weekly or monthly demonstration games where you can learn-by-doing (see above).
Learn the system as a group of novices As pointed out by Mike Wells, two (or three, or four) heads are often better than one. If you are struggling with how attacks of opportunity or critical hits actually function, try getting some (interested) others' interpretation of the rules. Conversations will often help illuminate your misunderstandings.
Practice executing the described actions yourself As described by Colin D, if you have trouble understanding a description upon reading it, try to actually create a few characters yourself, or run a mock battle playing both the heroes (PCs) and monsters yourself.
Try Googling your question/topic There are plenty of blogs/company websites/etc where common misunderstandings are addressed. See what a google search turns up.
Discuss your problems with sympathetic RPGers in stack exchange's chat room With the caveat that the patience of more experienced players can wear thin fairly quickly, there are plenty of chatroom inhabitants (myself included) willing to share their knowledge with you.
In the end, as has been pointed out, this is your game, so the rules work however you and your fellow players decide they work. It's important not to get bogged down in the minutiae and just enjoy the game.
I have always found it useful to act on the knowledge I just read, especially with complex systems. I find it helps me link all of the content together and helps me understand the system as a whole better.
After reading about character creation, try creating a couple characters. This will help you understand all of the equations and how the 'magic numbers' listed everywhere shape your character.
After reading the section on combat, try out some sample battles where you play both the monsters and the heroes.
This experience will show you the gaps in your understanding of the system.
When we first started we had a small group of friends (in my case 3) and just created characters after we all read the PHB. We took our time to work together to figure out the rules together. The rule book is not hard-set rules, but more guidelines. As a game master, it is up to you to interpret the rules. I like it when the GM works with us to interpret the rules. The first characters should be throw-away because as you learn, you'll want to make lots of changes. Maybe follow a couple modules so you can get the feel of the system before creating your masterpiece (if that is your idea).