You've probably seen knitting projects with cute little embroidered flowers on them. Those sorts of embellishments are commonly what's referred to as a lazy daisy: a very easy embroidery stitch that gives you a flower in no time flat.
All you need to make a lazy daisy is a really, really long strand of yarn (seriously, longer than it seems physically possible to use, you'll probably need it), a yarn needle and some knit fabric in need of embellishing.
First, decide where you want the center of your flower to be. Thread the needle and tie a knot at the end of the yarn, if desired. Bring the needle up through the spot that will be the center of the flower, from back to front, pulling the yarn all the way through.
Put the needle back through the work in exactly the same spot from front to back. Pull on the yarn slowly, and when the loop that's left on the front is the size you want your flower petal to be, bring the needle back up through the work where you want the end of the petal to be, and make a short stitch here over the petal yarn to tack it in place.
Bring the needle back to the front and repeat for each petal you want on the flower. It's a good idea to make your second petal the one directly below the first one you made, then make the two that turn the petals into a plus sign. That way if you want more petals between these four, it will be easy to space them evenly.
You can make these just about any size you like, and use just one or a series on a knit item. Finish the center with a stitched-on bead or a French knot.