I am a noob to all this myself and I found that when I first started the most difficult thing was to decide which 3D software I was going to use, IE 3DS Max, Milkshape, Blender Etc, Etc. There are so many. I personally settled on Milkshape as it was very easy to use (for me) and relatively cheap (25 Euros) + they give you a 30 day trial to see if you are going to get on with it.
It also depends on how new you are to modeling and how much money you are willing to spend on the software. Some are quite expensive, but there are free ones that are very good too
Once this is decided then you need to play around with the software creating simple models (I started with a block) and texturing them until you feel comfortable enough to start creating the items that you want to use in you medieval game.
A simple sketch or picture always helps as a starting point to creating any model.
Hope this helps as a starting point
I've got something to say
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It's better to burn out than fade away.