I am playing D&D for the first time, and working on being a GM at that. We had our first session today, and it was very fun and went very well. However, one of my players chose a beastmaster, and I'm not sure how I should treat his companion. Does it roll initiative and have a turn of its own? Or does the ranger "command" it with different actions during his own turn? I've looked through the tooltips for the class feature and things like that, but I'm still not really clear on how to control this.
Basically, your companion would act on your turn, much like conjurations and I believe summons. I briefly had one in my campaign and during his turn, the beastmaster would take move actions along with the companion (counting as a single move action) and he would activate powers that allowed the ranger and companion to attack as one (usually these were two attack rolls for the same power, but other powers were one roll for a load of damage or effects.)
As posted from the quoted section. Move actions can be done at the same time. You can give up your standard action to have the creature attack for you (unless using a power that allows both to attack), you can give up your interrupt action for the turn to allow your companion to Opportunity attack (useful if the companion is blocking an exit while you're elsewhere), and you can both go total defense even gaining what a bonus to the total defense bonus in what I like to call "The Buddy Cop bonus".
Hope that helps.
Edit: Forgot to mention, but the ranger rolls initiative on his own. The companion always acts on the beast master's initiative. Also, the question came up on what happens to the companion if the ranger is knocked out. The way we ran it is that the companion could still act on it's own, but it's restricted to the basic options as the Ranger is the one who trained it to do special moves in cooperation with him. I can't be sure that that's correct however, but I believe that "unconcious so it effectively poofs" is restricted to conjurations.
(Copied entirely from MP1 p41)