Folks who have been around a while will probably be able to tell within a few minutes that you are a newbie, with or without a visible flag. And the vast majority of them will go out of their way to provide you with whatever help they can, as long as it is within the limits of their character's role. Everyone who has ever played this game has been a newbie at one point in time, so believe me when I tell you that you are in good company. Use the newbie channel, ask questions in character, roleplay and enjoy yourself.

As an aside, I fully endorse incognito's statement below regarding extended periods of inactivity. This is extraordinarily frustrating for both mortals and Imms (mostly because we are impatient SOBs!). If you need a bit of extra time to review a helpfile or figure out the context of a certain command you are trying to use, that is just fine, but please preface this time of inactivity with a quick 'Please give me a moment.' This will go a long way towards mollifying your impatient veteran groupmates.

By the way, once you've played three or four characters into the mid 30s, or have heroed a character, you're no longer a newbie. Now you're the experienced player helping out the newbies!