I love premade bias tape! It's great to have a package ready to go and just pin and sew - but it's expensive when you really think of what you're getting. Not a lot of fabric for $1-$2. There are other limitations as most packaged bias tape is simply one color. Trust me though, it is quicker to just buy the package, pin and sew - but making your own really isn't hard at all.
I needed some red and white striped bias tape to create the pirate vests and make them 'pop' and scream 'pirate' and my hunt for pre-made striped bias tape failed and so I gave up and decided to make my own.
To make double wide bias tape all you need to do is the following:
Step One: Take your fabric and cut your fabric in 2" strips - if you want a little extra 'wiggle room' make it ever slightly more than 2" but I found that the 2" exactly works just fine. The width of your fabric is unlikely to be suffient for your needs so you'll need to cut multiple strips.
Step Two: Sew those strips together. I find it works best to do this first before you begin ironing so you don't have to go back and unfold and piece together and re-iron. (sorry I forgot to take a picture of this step) but sew them together like you would sew most things - using a 1/4" seam and then press the ends flat.
Step Three: Lay the fabric right side down and fold over the fabric by about 1/2" and press. Steam is your friend, use it liberally to really get the fabric to have the crisp lines.
Step Four: Repeat with the other side, leaving a tiny bit of space in the middle so that you can fold the bias tape in half.
Step Five: Fold the bias tape in half and press once once more and you're ready to pin it to your project!
Step Six: To pin your bias tape to your project, simply open up one side of the bias tape and pin it all the way around and get to sewing. *TIP* look at your bias tape, unless you're super exact (which I don't find is necessary) there will be one side of the folded in fabric that is shorter than the other, pin that side first. It will help prevent if you're doing a top stitch to finish attaching the bias tape from that stitch showing. Although if you're planning on hand sewing the bias tape to finish attaching this does not matter as much. :)
Step Seven: Fold over the bias tape and pin it down and either top stitch for finish or do a blind blanket stitch to finish by hand. (I am a huge fan of the top stitch!)
And wala! Your project has a nice finished look to it.