I see it happen time and time again... the officiant has a flower, or doesn't. There's an extra flower for a hired vendor, but someone in the ceremony doesn't have one. Today I'm talking to the brides and those picking out the flowers for their wedding - make sure you don't leave anyone out!
Your largest and most impressive arrangement should, of course, be the bride's bouquet! It's the showstopper, and is the final accessory of the bride's. There should only be one of these (duh!)
The bridesmaids will each have a bouquet to carry, which should complement the bride's bouquet. These shouldn't overshadow the bride's bouquet, can be different and beautiful in their own right. Often the maid/matron of honor(s) will have a slightly larger arrangement than the other bridesmaids, or have a different type of flower than the rest. Or, sometimes they won't! It's totally up to you, the bride.
If you're planning to do a bouquet toss at the reception, you'll also want to make sure to order a toss bouquet from your florist. They will make a smaller bouquet inspired by the bride's bouquet or in a fashion that you like. I would never recommend tossing your actual bouquet - it's typically very heavy, and even if you don't plan to do anything with it after the wedding, it's best to have something else on hand.
So now let's talk about what the other ladies should have! Moms, grandmas, aunts, and other women that are important members of the family will wear a corsage. These can be either pin or wrist corsages, it's up to you. If they're in the processional or have a part in the ceremony (more than just an assigned seat), then they should have a flower. This designates them as an important part of the celebration and allows them to feel included and involved in the day. I have also seen flower crowns for junior bridesmaids or flower girls, and small bouquets for the moms! Both are really sweet options.
For the guys, it's pretty easy - they will wear a boutonniere. The groom will have one, and I always think it's sweet when it has some sort of special feature that matches the bride's bouquet, but makes it unique from all the other boutonnieres! All of the groomsmen will wear a boutonniere (if they have a jacket, if not, it's more optional than anything) and they can all be the same, or all be different. The best man/men can have something a little different, or not! Again, it's up to you. The dads, grandpas, uncles, ushers, ring bearers, etc. that are a part of the processional or in the ceremony should each have one.
There's one tricky part to this - figuring out which of your "vendors" should receive a flower. It really comes down to who is a family member or friend, and if you are paying for their services, or under contract. If you've hired the officiant or ceremony musicians and they wouldn't be someone you'd have involved in your day otherwise, then don't get them a flower. If they're gifting you their talent or services, I would recommend getting a flower for them.
Ultimately, this is all up to you, but just know that who you don't get a flower for speaks just as loudly as those you do get a flower for. Don't use this as a time to highlight any family drama, or create any!
Another piece of advice - order an extra boutonniere and/or corsage, just in case!
As your wedding planner, it's my responsibility to double check all of the arrangements as they're delivered, distribute them, and pin/attach all flowers before the ceremony.
Who Gets What Flowers?
Bride: Bouquet, Flower Crown
Junior Bridesmaid: Bouquet, Flower Crown, Corsage
Flower Girl: Flower Petals, Flower Crown, Corsage (wrist)
Moms/Grandmas/Aunts/Cousins: Corsages, Small Bouquets
Groom/Best Man/Groomsman/Usher/Dads/Grandpas/Uncles/Cousines: Boutonniere
For anyone providing a service as a gift or in the capacity of a friend, a boutonniere or corsage is appropriate. This could apply to anyone gifting any service - music for the ceremony, the flower arrangements themselves, photography, etc.