I use 2 steps. Choosing the leaves is important. Do not use old yellowiing leaves, do not use young immature leaves. Use leaves that are mature size for their type and lush green. Even for variegated type, the green leaves will sprout better than variegated ones. Cut with one clean action with a sharp knife. If you struggle to cut , you have probably damaged some cells and the rooting will be slow. Fill an opaque container with clean water (not mineral water) and seal the top with aluminium foil. The reason you chose an opaque container is so that the distal cut end of the leave is not exposed to light. That way, it is encouraged to root. Poke holes in the aluminium foil and stick the leaves through these holes. Expose the leaves to indirect bright light but not sun light. If you have filled the container right to the brim initially, you won't need to look at it until 2 weeks later. If you do this during spring or autumn, roots should appear in 2 weeks, the latest 4 weeks. When you see roots about 0.5cm in lenght, you can plant it in soil:perlite:vermilite at 1:1:1 ratio and in a 2" pot. If you forgot about it and found it has grown to 2cm of root, I usually cut it back to 0.5cm before I plant. Roots that are >0.5cm are water roots... they might rot in soil and kill the plant. We want the short breathing roots only. Hope this is clear enough.... I have lots of baby plants this way.
If you want to use the office air-con but worry about the direct sunlight, you can go to Jian Guo Flower Market and buy this black netting to stick to your window. It's gonna look ugly, but will do wonders to your flowers.
I read this frrom a book on African Violets by a British author. She says that roots > 0.5cm become water roots. Water roots cannot change to breathing roots and but short breathing roots can become water roots if you put them in water long enough. Since water roots can't breath in soil, too many of them will cause them to rot and perhaps get infected. There are instances when I was too lazy to cut roots etc, but I find that if I have enough pertiles in my soil mixture, they do fine. I also sut them in clear plastic containers for 2 weeks just after potting.