It's worth knowing the basics before you start, see the following topics for a brief semi-technical explanation of the terms you'll encounter in the following tutorials
What is radiant?
Radiant is a mapping tool to create .map files, which can be 'converted' into .bsp files readable by Quake 3 based games using the q3map2 compiler.
A short tutorial showing the basics of using Radiant to make maps. Tutorial - Basic tutorial
How not to create your first room
There are a couple of great tutorials about how to get started making maps for Urban Terror, the best and most in-depth tutorial I know is for linux and is Rambetters Radiant Tutorial
These will show you how to get things sorted out and have a map running in just a few moments.
For a more detailed description of the process we've created a tutorial here which may take some time to follow, it's not meant to be a quick route but an in-depth guide to help you make maps well.
How to create your first room
A medium length (not too boring) giving a detailed tutorial on how to construct your very first room and perhaps your first map.
Detail and structural brushes
It's important to understand the way the compiler and the game deal with these 2 very different types of brushes. Knowing the difference may save you a great deal of time, make you make better maps
How to add a corridor/exit to your first room
Having create a single room you'll need to be able to get out into the rest of your map - this simple tutorial shows how to make a hole in a wall and construct a corridor.
How to create another room
This is a detailed tutorial explaining how to create a second room in your map, it also covers some topics relating to hinting.
In order to follow this tutorial you'll need to have followed the previous tutorial or, if you're lazy download the map created in the first tutorial Download here
How to create a door between 2 rooms
How to make a ladder
How to add water
How to make things breakable
Select the brushes you want to break (note that all selected brushes will break at the same time - if you want breakable windows, you will need to redo this step for every single window), open the entity menu by right clicking and then turn the selected brushes into a func_breakable. You can edit the properties of the brush by pressing N. See func_breakable reference for details on how to use it.
How to make an elevator
How to add a model
Right click to open the entity menu and select misc_model. This will open a file dialogue which allows you to choose a model. Please note that the default filter is set to MD3 and you may need to change that depending on your model. After selecting the model, you should see it in Radiant. You can drag it around and rotate it as you like.
If you'd prefer to follow a step by step tutorial on how to add a model, see the tutorial Adding a model to your map
See the misc_model reference for exact information.
How to make models and prefabs using radiant
How to build an entire universe in a single box
How to add Weapons directly into the map
There are 2 ways, one (the complicated) is this: You create a info_spawn, press "n" and write this (for a negev) in:
classname=ut_weapon_negev -says which weapon count=1000 -how often you can pick up the weapon and how much ammunition is in it wait=1 -time the weapon needs for respawn
Or you download the Urban Terror Mapping Package here and put it into your Radiant folder. You can select the weapons from the entity menu after restarting Radiant.
The full-list of all weapons and items which can be placed in the map you find right here