The easiest way to give a piece of clothing your own unique stamp of personality is to play with the proportions of length vs width.
Lengthening a pattern really is as easy as it sounds. Here are the three most important factors to consider before you start...
Things move around.... Mid thigh dresses I had assumed were completely modest when my arms were down, were suddenly much more risqué when I lifted them above my head. What many people don't realise, is that how much the hem of a dress will lift depends mostly on the armhole shape of the top. A sleeveless dress will barely lift at all, whereas something with a long sleeve kimono sleeve could lift up to 30cm or so. If your legs are as short as mine this is the difference between wearable or not. Therefore, applying the same length from a dress you made previously to your next top is not always going to have the same effect. Be sure to check out the movement from the shoulder/armhole area before you cut and add some extra length if you are unsure. You can always trim it off after.
Depending on how fitted your top/dress is, will determine if you need to adjust the width as well as length. Before you begin, its crucial to measure the widest part of your body (for most but not for all, it's a little lower than your hips and across your butt) once you have that measurement, compare it to the measurement of your top/dress hem and make sure your new dress is wider than your body measurement. To make sure it doesn't stick to your hips and visually look clingy, the hip measurement of a garment needs to be around 8-10cm in total bigger than your body measurement. Generally i like my clothes oversized and boxy. So a top like the LB Pullover didn't need any extra width added to it, as the hip Measurement was already 20cm wider than my own hips. Therefore to make the pullover into a dress, I simply extended the line of the side seams downwards (34cm to be exact) past it's original length and redrew my hem.
Can you still walk in it? If the top you have lengthened into a dress is narrow and long, can you still walk? I alway measure the hem circumference of my pattern, then I sellotape my tapemeasure into a circle that exact measurement and slip it over my legs to where I think the dress will finish and see if can walk comfortably without breaking the sellotape. You will look like an idiot when you do this, but no less of an idiot than you would look if you were wearing something you couldn't walk in. If it's too narrow to walk, you need to add a split somewhere, or widen your hem circumference.
Happy pattern hacking!