Keep your group small
Stick with smaller groups; 4 or 5 is a typical number. The larger the group the less time you can devote to each player. As players seek to ask you a quick question they'll feel ignored as you are busy fielding other requests.
Combat is a case where a small group is almost always better. The larger a group the longer the time between initiative passes; the players are spending more and more time watching and less time doing, the antithesis of role-playing games.
Outside of combat larger groups tend to be louder and more boisterous, it's easy for a quiet or shy player to be drowned out. A large group also encourages players to split up. A split group means you're juggling your attention between then, making the situation worse. Spare yourself the grief, keep your games small.