You came to the right place. The boards has a good amount of resources for players just starting out with the ISRP area.
The ISRP Pages - This is where you'll want to start out. This site contains information that will let you brush up on the ISRP setting used for Juxta (the Emporium), and what's on the menu at the Crossroads Tavern (which lies in Ford Keep, just outside of the city of Greyhawk).
The guide compilation - This is a listing of player written opinion guides that list some of the conventions of roleplaying used. Combat (quite proud of that one myself
), keeping a character's power level in check, ways to work with newer players (might work in reverse and show how to make yourself known), and more can be found here.
Aside from that, the big thing to keep in mind is Freedom of Destiny. While the ISRP is freeform roleplaying, there are limits in that each player decides what happens to their character and when. As long as actions that affect others are left open-ended and with plenty of room for the others around to choose what happens to their character, it should go smoothly.
As for what room is best for a new player, the Tavern is (or was last time I was in and active) usually more crowded than the Emporium, so it depends on how fast one wishes to immerse themselves in the chatroom.
Hope that helps.
