Inside out, Right sides together.
If you read enough sewing patterns you'll see the words "with right sides together" so often you'll start mumbling them in your sleep. Traditionally when we sew we make up a garment inside out, this means when we turn the garment right side out the seam (or the narrow strip of fabric next to the where we've sewn) is on the inside.
How to get rid of "unfinished" edges.
An unfinished seam or edge of a garment is where the fabric is rough, and has just been cut. An exposed rough edge never looks nice and can fray very quickly ruining your work. There are a few classic ways of getting around this problem.
Line the Garment
Lining a garment involves making a second version of the garment (normally in a lighter weight fabric) and then sewing them together, right sides together (see there's that phrase again). This sounds like a lot of work but once you get the hang of it you'll see some advantages. Often for a simple outfit it's quicker to cut out to copies of your project and sew them together than to try fiddling with finishing off the edges. Also lined garments tend to last longer. When lining remember that you're going to have to turn the garment right side out so you need to leave a small gap to pull the fabric through. For an idea of what you need to think about when making a lined garment check out - how to make a waistcoat
Hem the edge
Hemming simply involves folding the edge of the fabric over by a small amount, pressing, and folding over again. Then stitch in place. Perfect for the hem of a dress, or trouser legs or a toga/tunic. However this can be tricky for a curved edge, such as a neckline, arm hole or circle skirt.
At first glance bias binding looks just like ribbon.However on it's under side you'll see the fabric is folded at each side, meeting in the middle. Bias binding is made from a strip of fabric cut "on the bias" or at an angle. This means it can stretch and shrink on either side, letting you turn corners with it!
Wrap the raw edge in the bias and top stitch into place. This is a very quick and easy way to finish off neck and arm holes and can look great whether on club gear or school play costumes. I like to use a contrasting colour bias when I make petticoats.
Keep these simple points in mind and have a go at going freestyle on a simple project. you may surprise yourself!