Hi Siberys...funny I should be talking to you here outside the TQ forum but anyways I'll see if I have any pearls of wisdom for you (just in case you were wondering I have been DMing for around about 15 years on and off - from regular D&D days right through to now where I too have a group that meets once a week)
Now my first question to you is how much preparation do you do before each session? This can sometimes have an effect on the people that wonder off topic. If you have too much delay in storyline or interaction with the characters (e.g. scratching for encounters, or sorting through ideas) the off topic thing starts to happen. I have found that it is best to let most people "get it off their chest" early on when they arrive....then it is your job to maybe recap on what happened last week (set the scene). This hopefully will in turn make them switch their D&D hat back on because they will not want to feel left out.
Now for the people that like "Roll playing" more than the dice rolling and gaming asthetic of the game I would recommend introducing other subplots into the campaign where as there character gets to be the quest/party leader. This (in my experience) has forced the person who 95% of the time jeopardises all plot line to suddenly realise that he is actually given an opportunity to lead the group and this has proven to be a turing point for me as the DM. **One thing to make sure happens is that there is combat fairly early on where the "Roll playing" player is potentialy the target or the one that requires help from the rest of the team....this is usually the catalyst for realising that they need to work as a team.
The person that plays stand-offish but very detailed background characters keep asking him what he is going to do within the group. I have nicknamed these types of players "turtlers"...you have to be aware of them and get them involved otherwise they fade from existence and out of the gaming group.
All and all if you are still having difficulties get the players character stats e.g. Ability scores, AC, HP's, skill points and feats. This is so that you can see what each of the characters are good at and tailor make scenarios and events that forces them to make use of there skills etc. This basically making feel more attached to their character and hence probably putting a bit more thought into it.
Few other tips:
Make sure when your group is starting new characters that they role the scores in front of you (inc. hitpoints whenever they level up). This basically adds a greater sense of honesty to the game and will make it a lot easier for you down the track.
Encourage every player to state what action they are going to take. Even if they go off storyline or out into the left field always have something side encounters developed and ready to go. You can chose to make it so it eventually leads them back into the main story or keep it focused on individual character sub stories. But what ever you do have something organised as soon as you dive for the Monster Manual the off topic players will start wondering....you guessed it off topic.
Encourage everyone to own their own dice...nothing worse than swapping dice around and when it comes down to the basic guts of it if they are not willing to fork out a few pennies to buy a set of dice how can they be serious about showing up and playing their character each week...
Last but not least have fun. Make a campaign world, describe the cities in detail, make "bloodstained" maps of the region that they can hang on to, create history and enriched backgrounds to your npc's, cretae past events that devastated the landscape, make your own monster types.
But all and all have fun doing it. Most of the time I found that if I showed that I was really into it the other players 9 times out of 10 would get involved too...after all the DM is the story teller.
