Drawing a Celtic Cross

This is a popular style as it's fancy without being too overbearing. Fortunately, it's pretty easy to draw if you've practiced the Latin Cross design enough times. The main problem is getting the circle in place.

Using a grid can make this easier; just follow this pattern:

An example of making a Celtic cross using a grid

Don't want to use a grid? There's a solution for that too:
First off, follow the Latin Cross tutorial with one slight change. You want the cross itself to be fatter than usual. To do this, you should make the line drawn in step 3 roughly 150% the length of the smallest segment. That's the length from the tip of the line to the middle of the second segment.
Time to place the ring. The stipe already has a line down its center, so add a new line down the center of the crossbeam.
Divide the lines in the center of the last sections of the top three arms into three parts.
Copy those marks to the bottom part of the stipe. One way to do this easily is to draw lines coming down at 45 angles from the marks you just made.
Those marks show where the edges of your circles should go.
For an optional bit of extra flair, try adding circles to the corners of the box made by the area where the stipe and crossbeam meet.
Clean up your lines and you've completed your Celtic cross!