If there is one thing I would recommend over all other things (when it comes to managing an event) and that is to have all the information in one place.

Take invitations and responses to those invitations as a very good example.

You have created a list of people to whom invitations have been sent. You created / acquired the invitation and sent it to the recipient. But what do you do when people start to RSVP? And how did you ask them to RSVP more to the point.

I find spreadsheets are the easiest to manage. Have columns for first name / surname / name of organisation / address /

Then add a column for Yes / No; a column for special dietary requirements and a column if you have asked them to do something else.

Say for the sake of argument you are planning on holding a breakfast function, but are aware that some people may want to stay for a chat after breakfast. Most venues will provide a tea and coffee station, but these are provided on a per person basis, and costed accordingly. So if you don't ask them if they are going to stay - how do you know how many people to cater for?

When the responses start coming in - have the one central collecting point for them. That means you can tell at a single glance who is coming and who needs a gentle reminder.