Eyelets or "D" Rings
Picture Wire (Thin strings of wire plastic coated)
A general rule of thumb has been to measure your canvas about 1/3 or 1/4 down from the top and mark for the wire to be placed there.
Fastening is personal preference. Here is how I do it.
Step 2: Pre hammer a nail lightly to puncture a hole if required. Some frames use harder timber then others. Screw in eyelets or "D" rings.
Step 3: Measure the width of the inner frame from D ring to D ring and add desired excess and slack. Feed wire through loop. I add about 10cm to each side of excess.
Imagine a triangle made from the wire. The tip or point is where the nail in the wall will hold the painting. Add enough slack to create about a 2cm high triangle or as desired depending on your placement of the D rings.
Step 4: Loop wire through hole again
Step 5: Wind wire towards the centre about 5cm.
Step 6: At the halfway point of the excess wire (5cm) stop and wind back towards edge of canvas
Standard rule for galleries is to hang painting with a nail or screw or alternative hook (e.g. 3M system) at eye level. Now what is eye level??? Everyone is at different heights. Use your judgement. A rule I have used before is measure is between 150-200cm from the ground up.
Here are a few links which might be of interest to you about preparing hanging art
Presentation hanging of the artworks on the wall
Or if you are someone wanting help to hang your art, here is a website which offers an insight into how much it could cost if you hire someone to provide this service http://www.arthangingsystems.com.au/view/page/33.html