The ideas in these 12 items are not expected to appear as superbly original. Hopefully they will give a fresh perspective to your existing knowledge or experience. Buddhism is full of lists for the good reason that they do help us remember. My thought was that this list could provide the basis for your own, personalised version. It assumes that you enjoy teaching and enjoy the subject you teach so I have left FUN off the list - it's not really something you remember to do. I have used it, bent it, hacked and whacked it over the years - and this is more or less the result. Feel free to do the same.
1.

KISS - Keep It Super Simple. Be clear about the idea or concept that you are trying to get across with any particular exercise. Can you extract the core idea and write it down in one sentence? One word? If not, is it too complicated?
2.
ONE idea or concept should be the limit for each undertaking. This is really an extension of 1. but the point is worth emphasising. The 'undertaking' could cover a series of events but the principle is the same: 'Over this weekend I would like us to look at the idea of self-consciousness.' Within this idea there can be several aspects but be clear in your own mind of the connection between them.
3.
Make a list of key points well in advance. Giving an idea a name helps solidify the concept which gives you time to develop abstract thoughts in relation to a more tangible 'object'. Put the main concept at the top and the related ideas below. With big undertakings I have used the computer and set up a folder (main concept) with various sub-folders (related ideas) - or a spread sheet?
4.
Group identity is good to establish at the beginning by acknowledging individuals. Who are we? Names, ages, why are we here? etc. It is important to establish some trust, especially if the group is new, but it can be fairly brief initially - remember that the gathering is not exclusively a social one. Ideally connections are made through the various activities.
5.
A 'warm up' activity can be useful as it helps people to relax - especially those new to the group - but it is not necessary. It could be something quite unrelated to Buddhism. It can be time well spent or time wasted and is often best decided on the day. [see: Drama]
6.
Graduate activities, building complex ideas on simple principles.
7.
Keep your list-of-events handy and refer to it (unless you have a clear enough memory) at the completion of each section. You could even make it part of the group's property so everyone knows what they have done, are doing and what is to come. Some things are better kept 'secret' and you can judge how much you want to explain and how much to withhold.
8.
Clear decision making is a superb ideal - 'Now we will do this and it will take 15 minutes, and then we will do another interesting thing which will logically lead on to....' Ideals are rarely realisable but be clear (if only in your own mind) when a new activity is starting, when it has finished or when discussion or activity is being sidetracked.
9.
Flexibility is another ideal worth upholding. Allow the energy and levels of interest of the group to guide progress. If something is working really well - and you had thought to give only half an hour to that - can you be sure that the next planned activity will sustain attention. Can the next concept be readily incorporated into the state of the current one? What is the loss in dropping the times - or even whole activities - allowed in your plan?
10.
Stopping is allowed - if not essential. The energy of the gathering doesn't have to be one endless happening. The group might be full of beans, going wild, restless - but you can stop - take a few deep breaths - step back from it all - have a read of your events list - go to the bathroom; not necessarily in that order. The whole group can (be made to) stop; a well used bell is often useful here.
11.

Discipline has to come into it somewhere. To expect everyone to be constantly enthralled with your offerings is unrealistic - they will fidget, play about, make noise, etc (and that's just the adults). There needs to be some consistent standard of behaviour and mechanisms for those who are too far outside. Firm but fair. I could write a lot here but it is a bit outside the scope of this work.
12.
The Wildcard is essential. What was planned to take half an hour took ten minutes, everyone is restless, new people arrived halfway through, nothing is working. Something has to change. I usually go for something completely different - let's all stand on our head! (in robes I just supervise this one) let's go outside and find something hard, something brightly coloured and something soft. Intuition and spontaneity are the key.