Being a Wedding Photographer I see lots of different things, and different venues do have different "rules" regarding timings, and a lot depends on whether or not you are having a Church Wedding or a Civil Ceremony - and whether or not there is a drive from your Venue to the Reception Venue, or it is all in the same place.
There are two things I find that tend to run behind on the Wedding Day - Bridal Preparations and the First Dance!
So I thought I would follow along, with some helpful advice of tips and timings throughout the day, as this will help keep you as stress-free as possible.
Depending on your dress, and depending on whether there is a drive to the venue - aim to get in your Dress at least 1 hour before the ceremony! (Or 1 hour before the car is collecting you) this means if hair and makeup are running late, or something else is on the morning, you still have plenty of time. Your dress shop will more than likely to tell you that you need to "settle in" to your dress to make sure you are feeling comfortable before you walk down the aisle.
If you are driving to the ceremony, the car company will always quote you a little bit longer. Depending on the car, they don't go as fast as you think they do - or a Saturday when there's a football match? All these things need taking into consideration.
Most tell you to not be late - Church or Civil Ceremony, some have a little bit of wiggle room (by about 5 minutes!) but remember with a Civil Ceremony chances are the registrars will have to leave to go and officiant at another Wedding elsewhere, if you run too late you run the risk of not getting married at all.
When you leave the ceremony, and you are heading for reception drinks (or before you head to the car) your guests will want to speak to you, say hello and how wonderful you look and how happy they are for you. This is normally what your receiving line is for before the meal to thank everyone for coming - but it normally happens at this point in the day too - even if you haven't planned the time for it.
Depending on how long you have before you sit down to eat, the amount of guests, and also how many group photographs you are wanting - this is time that needs to be managed efficiently. The food cannot be put back, and depending on what you are having for dinner you cannot have anything that is over-cooked.
Whilst this time is when you want to get the beautiful pictures, but also mingle with your guests. Take this into consideration when you are choosing how many group pictures you would like. And always try and leave at least 30 minutes for photographs of you as the happy couple! Sometimes you are only given 1.5 hours at some venues (sometimes more, sometimes less) and sometimes that "minute" you would like can really impact on what you can and cannot get photography wise.
Getting people sat down for the Wedding Breakfast is the hardest thing - and most venues will want your guests about 15-minutes before the meal is due to be served. If you are having a receiving line find out what time they will want you for this from the end of the ceremony / arriving at the venue - as this will impact on the above.
The happy couple is announced in - but this means that whilst Cousin or Uncle has run to the Bar, and Auntie is at the loo - it slows things up as you will not be announced in until all your guests are seated.
Venues normally say that a 3-course meal for approximately 100 Guests should take 1.5 Hours. This can be pushed to 2-hours but a lot try to stick to the almost "30 minutes per course" which is plenty of time.
These too can either happen before or after the Wedding Breakfast. After is more traditional, however, it depends on how nervous people are for speaking.
You never really know how long people are going to speak for. I have had speeches for 20 minutes (Dad, Best Man, Groom), and I've also had them last over an hour. If you have them before dinner - some bellies may start to grumble!
The one thing with the evening reception I find that gets pushed back is normally the first dance. A lot of people plan to have it between 7:30-8pm - but if not a lot of evening guests have arrived, or some family members aren't back from their rest-time then people don't want to do it. I find that most people are doing their first dance between 8:15-8:30pm with a Cake Cutting just before - and then partying on before the evening buffet starts around 9pm.
Lots of different things can happen - and can cause your day not quite to go to plan - but it's knowing about them and trying to stick within timings the best that you can.
Here is a simple run-down of timings for example
Obviously timings will change a little bit depending on venues etc. If you are getting married at 12 - in a Civil Ceremony then it gives you the afternoon to do additional photographs depending on Bad Weather or some bad mishap (like a car breaking down!) that meant some photographs couldn't be done.
I hope you find that this helps with your timings and Wedding Planning :)