As well as organising the main activity you also might want to consider the following;
Signing in sheet: if you want to know who attended. If you think you might want to keep in touch with people, ask for their telephone number or email address but let them know why you are asking for this information and don’t share their details with anyone else.
Name badges: for attendees and organisers so that you all know who’s who.
Evaluation: if you want feedback on how well the activity went, how much people learnt, what they will do differently as a result of your activity etc.
Refreshments: depending how long your activity lasts, who is coming and whether you have a budget. Note: hot soup goes down well in winter months!
Assistance: don’t underestimate how busy you could be on the day. If you can get someone to assist with general tasks such as meeting and greeting your attendees, checking venue arrangements etc. then do so.
Signposting: If your activity is being held in a centre or large building, put up posters to clearly signpost your attendees to your activity.
Particular needs: be aware of any cultural, personal or disability needs of your attendees.