As with anything else, do not abuse the kindness of others. Earlier I mentioned that group in my graduate course. In the end we completed the project without him, and in order for him to avoid getting an F he had to implement the project himself with our documents. In recent years, it seems like more and more students are working while attending school. The responsibility of a job, compounded by the demands of a class schedule, may give a student stress and feelings of being overwhelmed while making the group as a whole feel awkward when meeting schedules are discussed.
Time management is crucial.
That way you can keep track of your work schedule, class schedule, and homework schedule. You can then allocate time and prioritize tasks accordingly. All students should use a calendar, but it will be essential for you. Don't overload yourself whenever possible. I can never say to not overload yourself at ALL costs, because everyone's situation is unique.