The biggest problem is time. It can often take several months to get enough kids interested to have a good group, and several months together to feel comfortable. However, even the most successful groups took a while to start. Be patient and keep trying to find people, they are out there. Other problems people have had are choosing a group name, picking a time and place to accommodate everyone, coordinating transportation for kids, and straight parents who don't approve.
Some groups meet regularly in one member's home.
Some groups move around each meeting to a different member's home. In the experience of other group leaders, once a week is too much, and less than once a month is too little. If group members are dependent on their parents to bring them to meetings, it may be necessary to talk with them directly. Try to be flexible, at least one group created more problems than necessary by setting the time and place for the meeting in stone. Groups of young people usually need a leader.