You can simply tell the learners what the rules are - you have complete control in this case, they are YOUR rules and it is your responsibility to enforce them. By letting them decide the rules learners have a greater commitment to keeping them. This latter approach sounds good, but it's likely that the rules won't meet your perceived needs: words like 'silent' and 'respect' and 'on-time' might be missing!
Better that Rules are agreed between teacher and learners, and best that they are established 'up front'. The age, maturity, size and purpose of the group is important in this regard: 'no mobile phones' might be less apposite in a class room of six year olds, than it is in an FE (Further Education, 16+) students, for example.
Rules should be simple (I recently attended a session where rules were no more than four words each, and there were only six of them), thus easy to remember; they should be written up in big letters on a classroom poster, and thus always to mind; and they should be written down as the class discuss what they understand by each, and are thus 'embedded' in each brain as they are accepted by the group.
Ground rules are all there to ensure appropriate behaviour and mutual respect. Key clauses concern not talking over others, listening to the teacher, arriving on time, and turning off phones - the agreed list should be the basis for order in the classroom.
Not talking over others is about respect for other people, its about allowing voices to be heard and enabling teaching and learning to take place effectively. Unfortunately ten minutes listening to Parliament in action or BBC Radio Four's Today Programme might lead one to suspect that talking over one another is the way of things
Listening to the teacher is about respect for other people - allowing classmates to hear, developing a skill sadly lacking in much of society, listening and learning. Listening so that you understand another's point of view, or the content of a teaching session. It's about remembering that we have one mouth but two ears and using the two channels in proportion.
Arriving to a lesson on time is about respect for other people (you see the common thread in ground rules that's unfolding here?). The teacher has a limited time to get a set amount of information across. It takes time to settle a group into a learning framework, and late comers disrupt that delicate dynamic.
Turning off phones is about respect for others too - again about disruption, challenging authority and spoiling the session.
Rules then are about establishing a respectful atmosphere appropriate to learning - the major problem being that we live in a society where the individual is lauded above society, and its all about me, me, me. Respect is a character trait in sad decline in the West, and it's interesting to read reports of the higher academic achievement coming out of schools in countries / societies where respect for others, the older generation in particular, is the norm.
Agreeing the rules together can be used as a good introductory activity with a new group. Writing them up keeps them to hand for frequent referral, and writing them down helps fix them in the learners heads. A well balanced and mutually agreed set of ground rules should enable the teacher to prevent problems occurring in their classroom.