I wouldn't bother with a stop knot, just use a couple of rubber rig stops - moisten them before you slide them to avoid damaging the line.
Stick a bead on afterwards, then your float.
Pencil floats are best for stillwaters as long as it's not too rough. Avoid the loaded ones. Attach it bottom-end-only, set it a foot or two overdepth and stick three or four swan shot on the trace about 18" from the bait.
When you sling it out, the float will lie flat on the water. Tighten the line carefully and it will cock. This is very sensitive, it will usually keel over when a fish picks your bait up, then bob and go under as it moves off.
On rivers you need a through-the-middle float, use a sliding bomb for weight, say a couple of ounces and again set it slightly over-depth. It's easier fished upstream, as the flow will tighten the float up.
There's more information on rigs and other aspects of pike fishing here: www.pacgb.com look in the fishing tips bit down the left hand side.