Here's what I know:
The Pinchers
The lowest (well besides self-cleaners) maintenance and the most intuitive. You just "pinch" the deadhead off the stem.
- Begonias
- Pansies
- Petunias (optional)
The Snippers
Here's where the tools come in - you use a hand pruner to cut the dead bud right before the first leaf.
- Campanula (can also be snapped or pinched)
- Heliotrope
- Nicotiana
- Roses
The Snappers
This requires you to "snap" the flower off at the base. It really only applies to really long flowers like geraniums that have a large head.
- Snapdragon
The Shear-ers
This requires the large scary shears to do some serious cutting. I just use my hand pruners since containers aren't going to grow big enough to justify that kind of blade.
- Campanula
- Snapdragon
The Self-Cleaners
These are the easy guys. Though it can be hard to resist the temptation of snapping off the dead plants, the rule is that these guys can take care of themselves.
- Bidens
- Calibrachoa
- Lobelia
- Verbena
- Wave Petunias
The Big Projects - Pruners
Then, some plants are so high maintenance that they require annual, complicated pruning in early spring:
- Clematis
Unknown
With the rest, I've been going with my gut since I haven't found any great insight on the worldwide web.
But, what to do with the deadheads? I'm not entirely sure. Sometimes, I just throw them over the deck. Other times, I test them out as fertilizer for some of the bigger pots, but I'm not sure how effective it is ....