As others have said, watch as much football as you can, whether that is on Match of the Day, on line or wherever.
Also, perhaps popping down to the local rec on a Saturday afternoon or Sunday morning to watch some grassroots football can help.
It'll give you a chance to see what the standard of football is in your area, and you'll also get a chance to see how other more experienced refs deal with positioning and certain incidents etc.
With the speed of making decisions, it does come with experience, but you'll also realise that you don't have to make instant decisions, it may not seem like when you start out, but you have more time than you think to make a decision.
Finally, if the ball goes out over the touchline or goal line, you don't know who it came off last and both teams are claiming it, give it with confidence to the defending side.
Even though one team will say you've made the wrong call, it's unlikely a goal is going to be scored directly from a goal kick, and a throw at least half the pitch away isn't going to affect the game too much.