The XML links everything together. Everything should be in a folder with your tileset name, the xml should be the same name as your folder, and it should look like this. Note that the red text is either a comment or it must be removed. Comments are in <!-- -- >'s.


<?xml version="1.0"?>

<tileset>
 <surfaces>
 
  <!-- Surface 1 ~ Grass -->
  <surface>
   <texture path="texture path" prob="these must all add up to be 1.0 it is the chance of this surface appearing"/>
  </surface>
  
  <!-- Surface 2 ~ Grass 2 -->
  <surface>
   <texture path="texture path" prob="these must all add up to be 1.0 it is the chance of this surface appearing"/>
  </surface>
  
  <!-- Surface 3 ~ Road -->
  <surface>
   <texture path="texture path" prob="these must all add up to be 1.0 it is the chance of this surface appearing"/>
  </surface>
  
  <!-- Surface 4 ~Stone -->
  <surface>
   <texture path="texture path" prob="these must all add up to be 1.0 it is the chance of this surface appearing"/>
  </surface>
  
  <!-- Surface 5 ~ Custom -->
  <surface>
   <texture path="texture path" prob="these must all add up to be 1.0 it is the chance of this surface appearing"/>
  </surface>
  
 </surfaces>

 <objects>
 
  <!-- Object 1 ~ Trees -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 2 ~ Dead Tree -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 3 ~ Stone -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 4 ~ Bush -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 5 ~ River Object -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>       
  
  <!-- Object 6 ~ Grass -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 7 ~ tortured -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 8 ~ Statue -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 9 ~ Big Stone -->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
  <!-- Object 10 ~ None-->
  <object walkable="is the object walkable">
   <model path="model path"/>
  </object>     
  
 </objects>
 
 <ambient-sounds>
  <!-- Sounds -->
  <day-sound enabled="true or false" path="sound path" play-always="wether to play always (false)"/>
  <night-sound enabled="true or false" path="sound path" play-always="wether to play always (false)"/>
  <rain-sound enabled="true or false" path="sound path"/>
  <snow-sound enabled="true or false" path="sound path"/>
  <day-start-sound enabled="true or false" path="sound path"/>
  <night-start-sound enabled="true or false" path="sound path"/>    
 </ambient-sounds>

 <parameters>
  <!-- Water Texture -->
  <water effects="true">
   <texture path="texture path for water"/>
  </water>
  
  <fog enabled="true or false" mode="the mode, 1 or 2" density="density of fog" color-red="#" color-green="#" color-blue="#"/>
  <sun-light red="#" green="#" blue="#"/>
  <moon-light red="#" green="#" blue="#"/>
  <day-night value="#"/>
  <weather sun="percentages of weather" rain="percentages of weather" snow="percentages of weather"/>
 </parameters>
</tileset>

That's the tileset XML. The objects and surfaces can have multiple units. For surfaces and anything else requiring you to give a chance of appearance, they must total 1.0 for all in that catigory. Object 10 MUST be the 'none' object and it MUST be walkable. In fog enabled, a good density of the fog is 0.005 - 0.025. Higher than that may end up with fog that is too thick. I reccomend setting the fog mode to 2. For sunlight, it should be 1's for all the colours, while night can be just under half of that or simular. The water texture should be a TGA and should have alpha in it, so that the water has a transparency to it.

That's all the catigories to making a Tileset. Now read the closing and you're good to go!