1. Your guests are people you are inviting to share a very special occasion in your life-perhaps the most special of all. You are asking for the honor of their presence (if your ceremony is at a house of worship) or the pleasure of their company (if your ceremony is taking place elsewhere). Thus, any "It's our day, to heck with what the guests want; if they can't cope then it's their problem" attitude has no place in your wedding planning.
2. Your guest list should be confined to human beings only. Dogs and any other animals need to stay at home (service animals excepted). In the case of service animals, they need to be firmly under control and not allowed to get loose under any circumstances. Your other guests need to leave them alone.
3. Spouses, fiance/es, couples living together, and SOs all need to be invited as couples to the ceremony, reception, and any pre- or post-wedding celebrations. Exceptions are parties such as showers or bachelor/ette parties for one sex only. Just as you are celebrating the formation of you and your fiance/e as a new couple at your wedding, you need to be respectful of their relationships and invite them together-even if you don't know or like one of them. The only exception is if one of them has threatened the lives or safety of anyone at the wedding. Each partner should be listed by name on the invitation, not as "and guest."
4. You need to budget properly for everyone attending. That means no tiered hospitality (some of the guests are invited for the entire reception while others are offered lower quality or less hospitality). It also means no cash bars in any shape or form and no closing the bar for a portion of the event to save yourselves money. See grumbledore's wonderful sticky about this:
http://forums.theknot.com/discussion/995381/cash-bars-everything-you-need-to-know-in-one-place/p15. Anyone invited to a pre- or post-wedding event (at-home reception, shower, bachelor/ette party, rehearsal dinner, engagement party, or any other kind of wedding-related event) must also be invited to the wedding itself. Provided they have been invited to the wedding, it is okay for them to attend the pre- or post-wedding event if they have declined the wedding invitation. Exceptions include private/destination wedding at-home receptions, showers and events given by religious congregations, co-workers, or clubs or other groups, as well as occasions held months after the event, but such occasions should be clearly designated "non-wedding-related."
6. Address your invitations only to those whom you are inviting to the wedding. If you are not inviting children, dates for single guests, or anyone else, leave their names off the invitation envelopes. If you are using inner envelopes, the names of everyone invited go on the inner envelope; otherwise, they go on the outer envelope that contains the invitation and any inserts. "Adults only" type-messages are rude.
7. If you are giving single guests the option to bring a guest of their choice, do your best to get the name of the persons they intend to bring. "And guest" should not be used unless you have made unsuccessful attempts to find out the name of a person a single guest intends to bring. You are not required to offer single guests dates, but it is a kindness. Who comes as a date is strictly up to the guest invited by name; you do not have any say in that.
8. If you send save-the-dates to anyone, you must follow up with a wedding invitation. If you send them to a couple who has broken up before the invitations have gone out, you are not required to invite the one you are not as close to. No other exceptions.
9. Unfortunately, you will need to contact any guests who have not responded by a reasonable RSVP date (about 2-3 weeks before your wedding; don't contact them before this date) to follow up with them and find out if they are attending. If someone who has not RSVPd shows up at your wedding, and you choose to host them (which is optional) you do have to be prepared to host them the same way you host guests who did RSVP in a timely manner; not to do so is rude. You are entitled, however, to tell such persons that they cannot be accommodated if they do show up.
10. This advice is being given with the intention of being helpful to its readers in avoiding unintended rudeness to your guests. While the etiquette police are not going to arrest you if you choose not to follow it, you will look bad and risk being side-eyed and losing important people in your life if you do not. It's ultimately up to you.