Wedding planning may seem like a very overwhelming task to embark upon when you first start to think about it. So what you need to do is to break it down into smaller more manageable parts. Give yourself a realistic timeline to plan your wedding. Unless you have a particular date in mind that you absolutely want to meet, then feel free to enjoy your engagement for a while and discuss with your partner what would work best as far as setting a date.
To have a vision of your wedding does not mean that you now should have an understanding of all the details and exactly how things should look and work out. All it means is that you have a framework that you both agree on and that you can go back to when you need to make decisions further down the line.
When you are ready to start attacking and looking at the details of the parts of wedding planning you'll most likely need to start by doing some research. The main reason to do this is so that you can include what you want to include and to exclude what you don't want for your wedding. But you want to find out about these things sooner rather than later so that you don't catch yourself with having forgotten a very important detail for the day of the wedding such as confirming your caterers etc.
Depending on what way of research you prefer you can either talk to people that have gotten married themselves, but remember that these people would have also designed their wedding according to what they wanted, not what you may necessarily want.
Hiring a professional wedding coordinator, only if its part time or one to consult with when you are stuck or need advice.