Trimming and repotting Euphorbias takes a little bit of care. It's mostly the same as any other plant that has gotten too big for its pot - you trim it back and put it in a slightly larger pot. But these tough plants have a secret weapon - the white sap - which stings like crazy. So be careful!
• Before you do anything, put on some gloves. I get the Dollar Store kind, three pairs for a buck and they do just fine for this. You just don't want the sap to touch your skin. No, it won't kill you or turn you into a zombie, but it will hurt. If you do get some on your skin, go wash it off right away. And throw the gloves away when you're done.
• Like any other plant that has gotten rangy, or "leggy", trim it back. I took about half of this plant off. Note that I put a paper towel nearby and I immediately transferred the cut shoots into a trash bag. The white goopy sap gets everywhere, and is sticky too, so treat it as if it were "hazardous waste".
Euphorbias are beautiful and tough. They do well even with neglect. So if you don't have much of a "green thumb", go ahead and get one, it will do great, especially sitting on a windowsill. But when you need to trim and repot them, be careful! I'll be leaving this out out in the shade today for a few hours to allow the cut ends to heal over a bit, and then I'll bring it inside.