No such thing as a stupid question. Ok now to answer ur question. I'm also using the canon S1, and the major bummer with it is that there is no AF-assist lamp, so in dim conditions, we can all go suck thumb as it basically can't see enough to focus on.
There's 2 work-around to this problem so far that I know of.
1) Zoom out to the widest angle 1st, this seems to let in more light, therefore helps the S1 to focus better. Once its focussed, slowly zoom in to frame the picture that you want. And when I say slowly I really mean it, jerking the zoom to telephoto will make the image out of focus again.
2) As was mentioned above, switch to manual focus, thot its kinda hard to be absolutely sure it's sharp on a 1.5 inch lcd, but it helps that the S1 magnifies the center to make things abit easier.
And in dim conditions, forget about using the viewfinder, as it does not brighten up like some other models, so its very dark. (Dunno why canon makes chose to omits such important features) Stick to the LCD. For taking night shots, or in dim conditions, switch to higher ISO, like 200 or higher. Slower shutter speed is usually a must, so bring a tripod along too to prevent camera shake.