What is the best way to stabilize a canoe for fishing?

Outriggers would help 

It depends on whether you plan to paddle the boat, or motor it.

 

If you plan on paddling, then outrigger position has to be carefully considered as to not limit the paddling stroke. Also with paddling, the normal lateral rocking of the boat while paddling can cause the floats to add drag, even if you rig the floats to be above the water when the boat is trimmed.  After giving it some thought, and you determine that outriggers would be a PITA, then the only way to "stablize" a canoe is by hull selection. Generally, the longer, wider, and or heavier the boat - the more stable its likely to be.

 

If motoring, then outriggers are a great way to go. I run my outrigger floats above the water when the boat is trimmed laterally so they add no drag (see photo).

 

If you go with outriggers, there are a number of "store-bought" models or DIY designs.

 

Thanks Goose!

I grew up fishing from a canoe, never even considered "stabilizing" it.  A properly designed canoe has both primary and secondary stability built into the hull, but they are still designed for someone sitting or kneeling, not standing.  We didn't fish standing up (I still don't), so if that's a requirement for you, I don't have a good answer.  I don't think I'd ever have one with outriggers.  Part of the attraction for me is the ability to get into and out of tight places, and they would just get in the way.