Think of height. You cannot put a 3 tall stage near the perimeter of most of the tents because of the lack of headroom.
Think of safety. Do not forget to "call before you dig" as most tent companies prefer to stake a tent into the ground.
Think of power. The placement of your tent may limit what kind of electrical options you may have. Although the middle of a field allows for a lot of space,you will probably need to look into getting a generator to provide electricity for lighting and music.
Think of layout. A lot of tent companies will be able to suggest a wedding tent size for you or provide you with a CAD drawing of our wedding. Even if they charge for the service,it is worth it to actually see the layout of everything for the peace of mind.
Many tent and party rental companies provide tents to festivals and fairs. Make sure that you ask for a "wedding quality" tent,or you may end up with a striped circus-style tent!
