I like to start with threatening them. I don't enforce peace unless they are willing to give both peace AND something else. If they ask for peace only, it's a big fat no. I want to crush them until I can snag some tech and that only happens when they're begging for peace (basically take over some cities, raze some if they're too corrupt, and send a stack of doom right next to a key city).
If they ask for techs and peace, "Throw you caviar in their face!" (Krusty the Clown).
Oh I crush them alright. It's most likely because I break peace deals too quickly. The AI learns after a short while that giving me something does nothing for them. I just think it's funny that I can be in the process of grinding down their forces and they come to me demanding a tech for peace.