First and foremost, BE CAREFUL WHEN YOU CHOOSE YOUR EMBLEM. If you choose the one and decide five minutes later that you'd prefer another one, it's too late. Once the emblem is selected, that is your guild's emblem permanently.
Secondly, make sure your guild members know when and where the emblem can be used. ONLY players who are either Level 20 and higher or who possess a tradeskill level of 400 and higher are able to have the emblem emblazoned upon shields and cloaks. Additionally, ONLY characters who meet these requirements can WEAR emblemized items. If a level 20 guild member gives a level 19 member an emblemized shield, the emblem will disappear as soon as the level 19 character zones. In this case, NO GOLD WILL BE REIMBURSED. So make sure your guild members are aware of this prior to hastily wasting large quantities of their hard-earned cash trying to be nice to lower-level guildmates.