Whether you're planning your own wedding celebration or attending someone else's special day, you'll know how important a wedding can be - one of the most important days of a person's life, in fact. Everybody wants theirs to be perfect, and after months of planning, the last thing you or the happy couple want is to have to deal with things going wrong. Of course, the unexpected can happen, but one thing you can control when you're part of a wedding is your own behaviour. The last thing you want is to ruin the day for the happy couple, and end your chances of ever being invited to somebody else's nuptials. Fortunately, help is at hand courtesy of former royal butler and etiquette expert Grant Harrold, speaking on behalf of Spin Genie, who has revealed the worst mistakes you can make at weddings and how to avoid them...(Picture: Getty Images/iStockphoto)

1. Showing up late

Hugh Grant's mad dash to the church in Four Weddings And A Funeral might be the stuff of movie legend, but just because we found it funny onscreen doesn't mean it's acceptable to do it in real life. 'The only person that can show up late is the bride,' Harrold says. 'If you’re going to show up late, don't go. Simple as that, and send your apologies for not being there.' In other words, make sure you allow plenty of time for your journey to the venue, in case of traffic issues or other delays. The only exception to this is if you know in advance you're going to be late for some genuine reason - in which case it's acceptable as long as you let the wedding party know in advance. Otherwise it's a no-no. 'I would strongly recommend you decline going at all if you know you’re going to be late,' Harrold adds (Picture Getty Images/iStockphoto)

2. Bringing a plus one without asking

So you've been invited to a wedding but your other half hasn't? Or you don't know anyone else who is going? It can be all too tempting to bring a plus one along, but unless the invite says you can, don't even think about it. 'Never take a plus one without asking,' Harrold explains, pointing out it's 'just rude' to show up to someone else's nuptials with an uninvited guest. 'You have to be permitted because the numbers, the catering, the diet requirements, everything's planned. Also, you've got to remember, there may be a reason the bride and groom don't want that person there.' If you do want to take a plus one for any reason - for example, if you've started dating someone and you'd like them to come along - it's acceptable to ask if you can bring them. But ultmately it's up to the happy couple and if they say no, you'll have to respect their wishes and attend alone (Picture: Getty Images)

2. Wearing the same colour as the bridal party

If it's a formal wedding, you can bet there'll be some kind of colour theme involved. But while such a fancy occasion might be a great excuse to dig out your finery, leave the bride and bridesmaid-type frocks to the bridal party. 'Don't wear anything similar to the bridesmaids, unless you're going to be part of the Real Housewives Club, where obviously they all wore the same outfits,' Harrold explains. 'You're not part of a band, this is a unique occasion for the bride. She's the one that should outshine everybody else, so don't turn up wearing anything that's going to distract from the her. I should know, because I went to a friend's wedding and I wore my kilt. Everybody was asking for pictures of me in the kilt, so never again!' (Picture: Getty Images)

3. Disrespecting religious rituals

Even if you're not religious and would be quite happy with a few choice words in a registry office for your own wedding, that's not the case for everyone. So if you're invited to a wedding in a church, synagogue or mosque, or to any sort of ceremony with religious rituals, then you should behave accordingly, dress appropriately (if required) - and definitely don't complain. Over to Grant Harrold: 'It’s disrespectful. If you go to somebody's wedding, you should respect the service, the rituals. It's their wedding, they plan it. If you're aware it's going to be a different type of wedding, and you aren’t on board with that, don't go. Simple as that' (Picture: Getty Images)

4. Causing a distraction

We all want to celebrate at a wedding, but the important thing to remember is it's the happy couple's big day - and while the reception might offer a great excuse to let your hair down, you should definitely be on your best behaviour during the ceremony. Shouting out, giving a running commentary of proceedings or letting a child cry or cause chaos during the main event won't win you any friends. And definitely don't monopolise the bride and/or groom after they've officially tied the knot. 'Everybody wants to go up and congratulate them after, which is fine, but what you don't want to do is hog them,' Harrold says. 'You've got to give them the space and let them meet everybody' (Picture: Getty Images)

5. Interrupting the speeches

Whether they're funny, serious, irreverent or emotional, speeches are an important part of proceedings. So the last thing you want to do is spoil them by jumping in with a few wisecracks of your own. 'No, you can’t do this,' Harrold insists. 'You do not start becoming the Toastmaster. You do not start becoming the master of ceremonies. You sit there nice and quietly, enjoy the time, enjoy the party, make the most of it, but do not interrupt the actual flow of everything unless you're the event organiser' (Picture: Getty Images)

7. Not buying a present

Like birthday parties, weddings are one of those occasions where buying a present for the celebrants is pretty much essential. But giving nothing at all? There's no excuse for that. 'Not buying a present is really unacceptable,' Harrold points out. 'You used to give something that they need, you used to get pots, pans, crockery, china, glassware, things for the home. But these days most couples have got a home together already, so they want a holiday or a contribution to their honeymoon. It's entirely down to what you feel. If the bride and groom have a wish list, that's great. Go with the wish list or something that's quite special for the couple.' That said, if you genuinely can't afford a gift, then it's better to be honest and tell the couple beforehand, rather than show up empty-handed, and consider an alternative gesture, such as offering to help with pre-wedding tasks, for example (Picture: Getty Images)

8. Being the person who complains

Finally, however well-planned a wedding might be, not every guest is going to be satisfied - and there's always going to be someone who complains about the event, whether it's the vows, the service, the food, the drinks or the music. While Harrold maintains those people always show their face at weddings, you probably don't want to get a reputation as that person. 'There's always going to be somebody at a wedding that can play Grinch,' Harrold admits. 'It could be a relative, it could be a friend, it could be the granny, the great granny, the great great granny or grandfather. The bride and groom should be aware how that could impact the day, if they are inviting somebody like that to the wedding' (Picture: Getty Images)