To have something useful we can do with our item, let’s add a recipe to turn two of our coins into a diamond. (You could probably do something better, like shapeless recipes to turn 10 coins into a diamond or a diamond into 10 coins.)

Here is the full class including the parts we added earlier:

package modderdojo.firstitem;

import net.minecraft.init.Blocks;
import net.minecraft.init.Items;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import cpw.mods.fml.common.Mod;
import cpw.mods.fml.common.Mod.EventHandler;
import cpw.mods.fml.common.event.FMLPreInitializationEvent;
import cpw.mods.fml.common.registry.GameRegistry;

@Mod(modid = "firstitem", name = "First Item Mod from ModderDojo by Michael", version = "1.0")
public class MyFirstMod
{
   @EventHandler
   public void preInit(FMLPreInitializationEvent event)
   {
      MyFirstItem first = new MyFirstItem();
      first.setTextureName("modderdojo:md2");
      GameRegistry.registerItem(first, "MichaelFirstItem"); // This name doesn't have to be same as unlocalised name, but no harm in them being the same

      // Recipe to turn 2 of our items into diamond
      ItemStack myStack = new ItemStack(first);
      ItemStack diamond = new ItemStack(Items.diamond);
      GameRegistry.addRecipe(diamond,
         "x ",
         " x",
         'x', first);
   }
}

Note that for built-in items like a diamond, you can write Items.diamond to get a diamond object to use in your  recipe code. Since our item is not built-in, we have to create an item object. We already have one called first in the preInit code, so we use that in our addRecipe code.