Everyone from your best friend to your fiancé's second cousin's dog will have an opinion about your wedding day. And you may say, out load or in your head, that you're going to stick to your vision and not allow people to influence you. But I'll be completely honest when I say that it's often easier said than done!
I have had countless conversations with friends and family, several who have said themselves that I shouldn't let anyone interfere, where ideas have been everything from suggested to forcefully pushed upon me! I truly believe that 99% of the time this comes from a good place, people want to give advice to help and show that they're interested. But it can get awkward when they're more insistent about something that you're really not feeling. This is particularly a problem when they're coughing up cash towards the big day. Whether they say it or not, you'll likely feel naturally obliged to allow those that are financially helping fund your day to have a say in it.
Firstly listen to what they have to say, they likely just want to show that they've been thinking about your wedding. If they're getting pushy it's OK to say you'll consider their idea...and then change the subject swiftly! Of course it depends on how important a factor it is, if they've got a totally different vision for your wedding dress and they're steering your bridal appointment off track it's probably best to not invite them to the next one! If it's about something you've barely considered maybe look in to it with them. If they're just completely off the mark it's best to just say it then and there and explain why their idea doesn't quite match up to your vision but maybe how something similar could work. Reminding them that you've got to be budget conscious is always a good route to go down as well and takes the responsibility off you. Everyone can sympathise with how much a wedding can cost!
Don't feel like a failure if you do give in to some things. I certainly caved on a few and it's easy to feel like a wimp for not standing up for yourself but really you're just trying to involve your friends and family in the wedding.