You're welcome.
Shadowslayer's points are also very important. DnD is a social game. The new player needs to feel welcome on a social level as well. All ppl in the 'old group', from DM to the other players need to understand that there is a mutual effort required to make this work.
I assume that a new player is being brought into the group becuase the group wants/needs to expand. All players and DM must agree on this. If some of the players think the group is big enuff already, adding players may not work solely based on the fact that the noob will feel that some of the players do not really want him/her to be there.
If all players and the DM agree that it would be fun to have an additional player, then this means that all ppl have to realize that for the session in which the 'new guy' is introduced, the ongoing game is 'put on hold'. You cannot simply go ahead where you left off. The noob has no background, does not know what happened before etc.
It is best to play a one-shot game, a side trek from the main campaign plot or a true one-shot with new characters all around, solely for the 'getting to know the ropes' for the new guy. The effort the others are putting into this (i.e. foregoing continuing the plot of the ongoing campaign) will also show the noob that all the others in the group are doing their best to let him/her catch on.
Furthermore, the other players must all realize that the noob is just that, a noob. No sighing at mistakes etc. the aim of the game is to teach teh noob, not to 'win' the game. So, if the noob makes a stupid mistake, the rest of the players should not act all irritated at it.
The other players should also try to find a good mix between letting the noob find his/her way and helping. If the players continually tell the noob what to do, then there is little fun in the game for him/her, on the otehr hand, if the old hands let him/her flounder, this is also not very nice. It is a fine line, but the 'old' players must try to walk it.
Furthermore, the old hands must allow the noob to shine as much as possible. Do not steal his thunder when he does something good. Compliment the noob when he figures something out which is cool. Positive reinforcement.
Just some more thoughts on the matter...