Pretty much what Rob said has been my experience. If you see the sky is darkening to the SW, you'll notice that the birds are flying about like mad, gathering bugs or seeds or whatever their food source is. Birds are a good indicator, because their metabolism is very high. If they miss a couple of meals, they will have trouble flying to get the groceries they need. You may see other animals out foraging, too. Hogs at the trough, big lineups at the driveup windows, etc. Fish are doing the same.
If you're on the lake, and the storm is comin', best be throwing something pretty big and horizontal, covering a lot of water. You'll note that when the birds stop flying, the storm has arrived. The fish may or may not stop biting, but I do think there will be a change in the aggressiveness and the bait should change. I've not had much luck fishing in the rain. You may notice that here, when it's raining, it's usually cold. In other parts of the country, a summer rain may be a good thing. I haven't a great desire to fish in the rain, but when I have, it wasn't good.
While I have had good results fishing as a storm approaches, the timing has been difficult, what with taking some time to get hooked up and ready to go, drive to the lake, get launched, etc. While the TeeVee shows seem to think high pressure is bad, I have not found that to always be the case. High pressure cells come in here and can stick for weeks, deflecting storms away. Stable weather is good, so strong high presssure cells are good, but you then have to fish early/late, or night, and targeting SM is a better bet. In my experience.
C&R, Steve
PS: Dipsport (sic), I saw you at the meeting, but was in middle of counting out $. Wanted to say "Howdy", but $ gets my undivided attention, ya know. So, a belated "Howdy Do". Don't be such a stranger.