Know what colors your wedding is themed around. This should not be a problem for brides but if the groom is taking on the task of ordering the invitations, he should definitely collaborate with the bride or the maid_of_honor to ensure no mistakes are made. It would be a travesty if the wedding colors are pink and mint green and the invitations are ordered as lime green and coral.
One of the most important aspects about your invitations should be legibility. You want to make sure your guests can read the writing. Consider this when choosing a font in contrasts with colors and patterns. For instance, avoid light ink on light backgrounds and vice versa. Your text should pop off the paper when guests are reading. Be careful when choosing overly scripted typefaces. Word your invitations eloquently with listing whoever is hosting your wedding first. Traditionally, this would be the parents of the bride. Make sure to spell everything out, including the date and time of the event. You can even give your wedding invitations a traditional feel by adding a request line after the host's name.