How to create a "stained glass" quilt
If you don't know what a "stained glass" quilt is, or  haven't a clue how to go about making one, here's some basic, easy to follow (I hope), step-by-step instructions...
First, there are two key elements to creating the stained glass look - 

    1. Choice of fabric: It's important to select fabrics that mimic the appearance of glass - a mix of bright, vivid, almost translucent colors with a few paler, more opaque ones will give your piece interest and depth (and remember fabric has two sides...if you're having trouble finding fabric with the right "opaque" look, check out the under- [or wrong] sides of those brightly colored ones). Search also for patterns in the fabric that either resemble those you typically find in stained glass... ripples, streaks, marbling, etc....or are small enough to not be overpowering or distracting....for example, tiny flower prints, dots, little swirls, etc. 
(*check out for a look at some beautiful marbled and hand painted fabrics. I also like Moda "Marbles" and the "Stonehenge" line by Northcott)
    Light weight cotton or cotton blends are best. Try to avoid fabrics that fray easily, but if you want to use a bit of satin (I used some in my "Hearth & Home" piece for the moon and some sections of sky) or similarly fragile fabric, get a tube of "Fray Block" to help minimize those frayed edges. It really works!

     2. Lead line tape: This is what separates this particular technique of stained glass/Celtic  quilting from the rest and gives the finished piece its "pop".  As far as I know the kind I use (a flat nylon braid - not to be confused with bias tape) is not available in retail stores, and the only places that I know for certain are carrying it are on-line, both here and at (link above). They have it available in both nylon and polyester 12 yd. lengths for around $10. They also offer it in green and white, polyester only ($11/pkg).
Second, there are a few necessary tools and products to have on hand - 

1. a pair of sharp fabric shears: if you're an experienced quilter I'm sure you already know this, but for the novice let me fabric shears. Anything less is going to result in frustration.
2. a steam iron: you're going to be tracing, cutting out, and glueing down fabric pieces of all shapes and sizes. Wrinkles and creases will, again, just result in frustration.
3. a wood burning tool (or iron, or candle, or lighter): when cutting the lead line tape (remember - it's nylon) you'll need to seal the ends with heat to keep them from fraying. See my Help page for more info.
4. a "sixth finger" tool: this is extremely helpful when maneuvering the lead line tape around circles, making folds, lifting and tucking, etc. Most fabric retail stores will have these available among their quilting notions. In a pinch you can also use a toothpick, tweezers, or similar instrument.
5. Fabric marking pencils or chalk: you'll be tracing off a pattern onto fabric, so you'll need a couple of water soluble marking pencils - a light one for marking on dark fabrics and a dark one for the light fabrics. 
6. A roll of masking tape: for taping down your pattern (and fabric)
7. Some water soluble "tacky" fabric/craft glue: for temporarily securing both your fabric pieces and the lead line tape - just to hold things in place until you're ready to quilt.

Another tool that's extremely helpful (but not absolutely necessary) is a light box for tracing over your patterns. You can purchase one on line or at any arts & crafts store, but they can be a little pricey - especially the larger ones. They're also reasonably simple (and cheap) to make.  Here's an example of a home-made one:
Front/top view: a piece of frosted glass (real glass, not plexi) rests inside a wood frame on top of a box that's slightly angled - about 30 degrees (but doesn't have to be)
Rear view: a simple  flourescent fixture is secured inside the box; an extra long electrical cord allows added maneuverability; and a switch on the cord placed within arm's reach makes it easy to turn on & off
My husband made this one for me years ago and I've gotten a lot of use out of it. It's a bit small (the actual glass surface is 12" X 18") but I manage to trace even the largest of my patterns just fine on it by shifting the pattern around and tracing small sections at a time. If you think you might like to try making one, there's a few things to bear in mind: A) use only flourescent fixtures; incandescent ones get too hot, B) the larger you make the work surface, the more light you'll need - either put in a bigger fixture or use more than one, and C) be sure to build the box deep enough to allow at least 6" between the top of the fixture and the under(frosted)-side of the glass. If you put the light source too close to the glass it can be annnoyingly bright; the light coming through the glass should be comfortably diffused and evenly distributed.
Creating a stained glass/Celtic design quilt using nylon or polyester leadline tape, step by step....
Start by taping your pattern down to a light source - either a light box or large, preferably sunny window...
Place your fabric over the pattern and trace (according to directions that came with it, or start with the background/bottom-most layer) Always make sure the side of the fabric you want to show is facing up!!...
Fabric will tend to ripple and shift as you trace, so use your other hand to hold it in place (as well as you can), and trace with short firm strokes
Use a ruler or simlar guide to trace straight lines
Tape the fabric down on top of the pattern whenever possible to keep it from shifting

Repeat this procedure for the next (and consequent) layer(s). Trace, cut, and glue down each layer/design area/fabric color as you go along.
When you cut your shapes out, make sure to cut just outside your trace lines. 
(see photo @ left)

The reason for this is anyplace where two fabric sections meet will need to overlap in order to ensure everything stays put once you start stitching/quilting. You'll also need a narrow (3/16") space along each edge to run your lead line along. Remember that once you start stitching you're going to want thread to grab every layer of both fabric and lead line. 
Secure your fabric pieces with "tacky" glue using  just a few well placed dots...
If you're gluing a rather large piece, position it first without glue, then fold over the top half, put down your dots of glue, and carefully smooth it back into place, moving from the bottom/center up.

Repeat for the bottom half.
Once you have all your fabric pieces glued in place, you're ready to start applying the lead line tape. If you'll be using a wood burning tool to cut it with, secure it well to your work surface and plug it in to start warming it up.
Please exercise care and common sense!!! The working end of this tool gets extremely hot - don't burn yourself, and keep children and pets far away. 

(my own cat is phenomenally stupid around this tool, but I never leave it unattended - no singed whiskers...yet)
If you'll be using a candle or lighter, have them nearby & ready....and again, caution and common sense!

Start by measuring out a length of tape.  Pick an edge you want to outline, place one end of the tape at the starting point and run it along the edge of the fabric you'll be securing it to with your fingers until you reach an end point, like so...  
Then mark where you want to cut it with your fingers...(or fabric chalk)
Bring it over to the cutting tool and carefully press the tape against the heated edge...
The edge of a hot iron can also work, but be aware that sometimes residue from the melted nylon might get left behind.

OR....snip the tape with your shears and lightly singe the cut ends with the flame from your candle or lighter.

Now you're ready to glue it down. Start by putting down a thin bead (or line of small dots) of tacky glue...
Then press the lead line tape down on top of it...
As with learning any new craft, it takes patience and practice. You might feel a bit awkward at first, but as you work you'll develop a knack for it and eventually come up with your own technique for doing it. 

The great thing about this tape is its flexibility - you can fold it over itself to form a point, as shown here... TIP: before folding, apply a few dots of glue on the tape where the fold will be. This helps secure it a little better.

It conforms beautifully to curves (even small circles!) with just a little nudging and stretching.

You might occasionally need to do some lifting and tucking of ends - this is especially common when doing Celtic knotwork, because of all the interlacing. This is when that "sixth finger" tool can really come in handy (no pun intended). 
TIP: apply a dot of glue to the end of the tape - on top and underneath - that you'll be "tucking" under. It'll stick better.  
And TA DA! You're ready to start quilting!

Choose a backing fabric, cut your batting, and proceed the way you would with any other quilting project. Quilt over all the lead line tape using either a zig-zag or double/parallel stitch (a single line down the center of the tape is not sufficient) and anywhere else you like, then finish off.

I hope you found these directions  helpful. If you think I missed anything or could be clearer on a particular matter, let me know with an e-mail Good luck with your project!