General manual handling techniques work well. i.e. keep the load as close to you body as possible, keep shoulders and feet pointing the same direction (don't carry the frame to one side with both hands as it causes you to twist).
Team lifting is relatively easy with frames, one at each end, which is our usual method.
If you have the option of moving them unglazed, then do. We tend to send the glass separately on most work, and have the glass units clearly labelled with their weight. The glass tends to be the heaviest element, unless you are using some serious reinforcing in the frames.
Send the anxilleries (handles etc.) separate too if possible, to further reduce weight.
Ensure all fabrication tables are at a sensible height, adjustable tables are great, but expensive. We find it easier to just keep workers to their own stations, set up with them in mind.
If possible with larger frames it is better to just push them along the floor (assuming you have a decent floor that won't damage the profiles), rather than lifting them.
Use stillages on wheels to move large quantities of windows around, preferably with a means to secure the windows to ensure they won't topple.
If you do need to glaze a window with a heavy glass unit it is a lot easier to do it upright (read as with a slight lean), as it keeps the glass unit close to the body better than a horizontal glaze.
Glazing robots are available, although bloody expensive, if you routinely move very large glass units. These can easily lift unit from vetical to horizontal of 250kg plus.
I, personally, normally try to carry them with one hand to the side of my body (normally with another in the other hand to balance me up). I find the centre of gravity and lift using the usual methods. If placing one on a bench I usually ask for help and lift one person at each end, unless it it is a small frame.
Feel free to pm me if you need some more of the controls we have, alternatively feel free to pm me with your own tips, since it was a problem I too faced when I started, and had to muddle through the best I could.