LONDON — Don't give the queen a friendly hug and don't tweet from the church.

That's just the start of the advice being offered to those attending Britain's April 29 royal wedding.

St. James's Palace says the guest list is an eclectic mix of European royalty, military personnel, charity workers, diplomats and friends of Prince William and fiancee Kate Middleton. Some invitees will have been born into families that teach children to curtsy as soon as they can walk, but others may need a bit of help navigating the etiquette and protocol that such an important day demands.

Anyone who is invited to the royal wedding will be given detailed instructions on how and when to arrive at Westminster Abbey, where the wedding is being held.

The first rule: Don't be late.

“The queen should be the very last person to arrive at the church before the bride and her attendants,” said wedding planner and etiquette adviser Sarah Hayward. “At most weddings, guests are asked to arrive around 20 minutes before the ceremony but the royal wedding will obviously have several important guests and very high levels of security so give yourself plenty of time to get there.”

Next, choose an outfit that blends in.

Women should wear a dress — not too short, not too skimpy and certainly not white. Most British women will complete the look with a hat or a fascinator — a small feathered or jeweled hairpiece attached to a clip or a comb.

“Never ever ever do anything to draw too much attention to yourself,” said Hayward. “It's the day the bride shines.”

Men in the armed forces should wear a military uniform. Male civilians are asked to wear either lounge suits — business suits by another name — or a morning suit, formal attire that includes a long jacket and a vest. A tophat should be carried, not worn, inside the church.

Couples should remember they will be seen together.

“Often you see a husband and wife who look like they are going to two different events,” said William Hanson, an expert on protocol who gives lessons around the world on proper behavior. “One person will be in something that looks like pajamas and the other is in black tie. You don't need to be color coordinated but do think about how your outfits look together.”

Guests may be asked by security to leave their cell phones outside the Abbey, but if they aren't, they need to make sure a ringing phone is not heard by millions during a service broadcast live around the world.

“The ultimate faux pas would be to have your mobile phone go off in the Abbey, even if you had ‘God Save the Queen' as your ringtone,” Hayward said.

Tweeting or updating your Facebook status during the day is also bad manners.

After the morning ceremony at the Abbey, some 600 guests are invited to a reception at Buckingham Palace, where the food and drinks are sure to be amazing. Hanson advises guests to accept the offerings politely — but don't gobble, don't gulp — and for goodness sakes don't get drunk.

“Sip your drink, don't gulp it and always be aware how much alcohol you can tolerate,” said Hanson.