If you have a larger hip to waist ratio, it's best to not have a maxi skirt that is too full with gathers around the waist, which will make you look larger:
An A line skirt such as this one, which skims the hips, is better:
If you are petite (under 5' 3"), a pattern such as the one above will be too large for you, so if you want a pattern, stick to small scale ones.
With a maxi skirt, it's ok to wear a top outside of the waistband, provided the top is not too long, otherwise tuck it in to the skirt but be careful it doesn't add bulk where you don't need it!
You can wear almost any shoe with a maxi skirt as they are not that obvious under the length of the skirt, so flat sandals, wedges, trainer type shoes or ballet flats are all fine.
Midi skirts are a little trickier to wear than maxis because of where the hemline finishes. Try not to end the hemline at the widest part of your leg, which is usually mid-calf, so just below the knee or lower than mid-calf are better.
Proportionately, tucking your top into the waistband of the skirt with a belt on top if your waist is slim enough is better than wearing it outside, as it looks neater and helps to avoid the frump factor of a long top (or a baggy one!) over a long skirt.
For shoes, trainers or trainer-type shoes (as in the photo above) are popular to wear with midi skirts in the summer but I would avoid them if you have thick ankles. Ditto for ankle strap shoes, which add another horizontal line across your foot/leg, thereby giving the effect of shortening your leg.
In winter you can wear knee length boots or ankle boots with matching tights to the boots. If your midi skirt is on the 'shorter' side then heels look better than flats as they elongate the leg.
This blogpost by Amber McNaught of Forever Amber is a great mine of information on the subject of how to wear a midi skirt http://www.foreveramber.co.uk/how-to-wear-a-midi-skirt.