At the start of each meeting, ask members for an update of where they are in terms of accomplishing their goals in order to make sure everyone is on track. If goals are too challenging, in other words impossible, they will be detrimental to the group because they will drastically affect the morale and confidence of the members. Don't be afraid to confront people who are not adhering to the goals set by the group. They may have good reasons for not pulling their own weight or they may just be lazy. Either way, the group cannot function effectively if all members are not contributing.
Goals are important as they provide structure but they are just guidelines.
Some situations require that you renegotiate your goals and you, as a group, must be flexible enough to do so in order to successfully complete the tasks at hand.