Jamming may seem to be easy for the inexperienced: Play anything which comes to mind and job done? Almost, what about if you jam with others, and whatever you play needs to be good and solid for others to understand and work with?
The key to all jamming is: Be clear with your ideas, keep your ideas simple and solid at the same time, be able to put a rhythm underneath anything you play (the simpler your ideas, the easier this will be).
Most beginners will play an idea, next time this idea will be different, third time idea will be different again and not a solid as the first time. Why is this? Probably, because people cannot hear their ideas in their head before they play, a bit like thinking aloud while talking. Not bad, but do this when you are on your own, when you jam with others make sure you know your ideas. If you are only starting out, keep your ideas simple—logical, since your vocabulary and technical skills may be limit at the moment, but still, you can jam and should really—–
The advantages of being able to jam are enormous: You can generate ideas which may kick-start new songs, you will learn to vary your ideas and increase your vocabulary.
The danger of jamming is that you will enjoy it too much, and you will end up jamming, and jamming is the only thing you do. Not bad, but since time is scarse you may also need to keep time free to learn new songs and work on technique and other skills.
Enjoy your jamming and hope to catch you again soon,