Make a list of everything you will need to bring with you on the big day. Gather everything in advance and put it in one spot so that you don't have to search for an essential item at the last minute.
Keep an online database or spreadsheet with the names of all invitees and RSVPs. Use the same list to note gifts given and thank you notes written.
Keep a binder or folder with images and ideas. This can be a physical binder or an online folder.