Working out the guest list is often put off until later, but it is essential, starting with a first draft that will help you choose the appropriate arrangement of your wedding, from the location to the catering.
Usually the list has three parts: family, friends of the bride and/or groom and other friends you have in common. Remember that your wedding will be more beautiful if all the people you love are with you. So remove third-cousins twice-removed and work colleagues that you only ever say hello to.
Remember that etiquette requires that you extend an invitation to the partners of your guests, although you can choose whether or not to invite the children. Keep in mind the demands of young guests: usually you would have a menu designed specially for them and a reserved table for them, as well as entertainers and nannies …
Final advice: do not invite your ex in order to not create any inappropriate embarassment or tension on such an important day.