Should I stir my sourdough starter before measuring? I'm new to using sourdough starter and some directions aren't very clear. I'm not sure if it needs to be stirred down before I measure for cooking and for feeding it. I've been stirring down the starter before measuring both when feeding and when cooking with it. Is that the right way?
Also, I've only been keeping 1/2 cup of starter to feed, adding 1/2 cup water and 1 cup flour. If I keep more, do I need to increase the amount of flour and water I add?
Rather than worrying about whether you 'stir down' the starter before measuring by volume, you should really be measuring by weight. Kitchen scales are cheap and incredibly helpful, especially for any kind of baking.
Regarding feeding: there are almost as many different feeding ratios as there are sourdough starters. None of these are set in stone. A common  ratio is 1:1:1 starter:flour:water, again by weight. Thus, if you keep more starter, you feed it more.