Don't force yourself onto her hands If she's bored. Or eating dinner - that's just stupid. While there's no perfect moment, the usual auspicious ones are when you're standing side by side, have your hands free, walking her home or at a movie /concert.
This only works when it's really cold and you're walking or sitting outdoors. it works better when she's not wearing gloves. Simply hold her hands (gently!) and say "It's really cold." in a sad voice. If she doesn't take away her hand in a few minutes, it's a win.
The Coded HandHold
If you hang out a lot with her, teach her,with a mischievous-kid tone some messages, somethingsecret and naughty.
Playful Hand Hold
Guide Her Way