Technically there is no correct answer to this, you can do whatever you like in any order if you so wish, but I would recommend taking a logical approach to planning your wedding.
To begin with we sat down and decided what we wanted:
* Civil or Religious - Civil
* Big or small - since we have very little family it's a small affair
* Budget - realistically how much would we be thinking we should spend?
* When - We opted for April 2010 (originally we wanted the 10th, but someone else had booked the hotel that day!!)
* What style of wedding - this was primarily my area, bless him but my other half has no idea and lets face it I don't think I would have trusted him.
*Guest list - List A, then list B and then anyone else we could think of lol
* Attendants - Who do you want as bridesmaids, best man, flower girl, pageboy?
Once some of that is out of the way you are well on your way to planning your wedding. The trick is to keep a list or even a notebook of ideas that you can look over and discuss with your other half.
And girls, note that sometimes your other half might just say "uh huh/whatever you think/ you decide...etc etc" it's not that they aren't interested, it's that you are often more excited about the day than they are. To them it doesn't need to have ice sculptures and a dove release, all that matters to them is that they are marrying the woman they love, whereas we girls want EVERYTHING to be perfect and do not in any circumstances want to give our future mother in law anything to moan about!!
I would advise booking your venue and registrar/minister as soon as you can to avoid disappointment. When we booked ours it was roughly a year and a half till the wedding (maybe more I just can't count!) and there were so many things booked already!
There's nothing to stop you asking for quotes with over a year or more till your wedding, just explain that you are merely making inquiries as you are working out your budget and would like a rough figure to work from. But do remember that prices are likely to rise year to year so things may not be the exact price you were quoted 9 months previously.
I'll make up a short what to do and when to do it list and stick it up here to act as a guide to work from, just remember that no one list is perfect or right, there are so many out there and they are only what one person feels is the best for them. You should do what you want to when you want to, so if that means you want to be like me and well organised then good on you it will save you stress and aggravation closer to the wedding. However if you prefer to wait till later to start your planning there is nothing wrong with that, everyone is different.