Let me try my hand at a basic hud making tutorial.
I will use Gimp as the program simply because that is what I use.
First,you want to fire up the Gimp.
Left click on File and then on New.Pick the length and width of your hud and click on OK.
Choose a color by left clicking on Dialogs and then on Colors.
Then left click on tools/paint tools/bucket fill to make your hud the color you picked.
Then left click on tools/selection tools/rect select to select a rectangle.
$Make a rectangle where you want the number of lives you have left to be.
Then click on layer/mask/add layer mask.
Click on selection/invert mask/ok.
Then left click layer/mask/apply layer mask then left click anywhere to select none.
Go back to the "$" above and repeat for the lives.
Change the foreground color by clicking on dialogs/color.If not your text will be the same as your background color and you won't see it.
Now click tools/text.
Left click somewhere around your first box and type in "LIVES". Hit ENTER and then close the text box.
Left click somewhere around your second box and type "HEALTH".Hit ENTER and close the text box.
Note:If you are displaying something other than lives or health then type that.
Then left click on file/save as.Call your hud whatever you want.Just make sure it ends with .dds.Then save it where you want to save your hud.
You have just made a hud.
Attached is the pic of the hud I made.It's not the best looking hud but it will give you and idea.
Once you get the hang of making them you'll be adding borders, multiple colors, and other crazy stuff.
I hope this helped.