How much directional control a skid provides depends a lot on what type of skid it is.
The Tiger Moth in my avatar has a 'spoon' shaped skid, which provides some control mainly because of the drag that comes from it. The Tiger has no brakes, so this, and the rudder are the only directional control you have on the ground. The spoon is attached to, and moves with the rudder so is steerable, although not very effective. If you are travelling slowly and need to change direction, you need to add power to get any authority from the rudder (it is very counter-intuitive when heading for an obstacle to use more power to avoid it!)
WW1 types typically had non-steerable skids with a 'blade' fitted vertically which dug in to the ground and provided a lot of stability on the ground, but also a lot of drag. To get these aircraft to turn, you need to put in full rudder, forward elevator (to take the weight off the skid) and a burst of power. I know operators who have removed, or ground down the blades to make taxiing easier. Your blade won't last long if you land on seal, even grass airfields tend to wear them fairly quickly.
Either way, both types give fairly good control for take-off, especially given that the tail comes up pretty quickly on take-off. As Flyboy mentioned, its mainly the rudder (and maybe brake on more powerful aircraft) that you use for directional control.