First off, the answer depends on weather conditions. I'm throwing different lures depending on if it's windy, sunny, overcast, pre frontal, post frontal, day, dusk, dark or if there was a over night water temp change that might effect bass behavior.
That said, if it's summer and I'm already on a lake I've never fished, without having done any research on it, I'm looking for the obvious. Cover like weed beds, lilly pads, rip rap, laydowns, docks etc. etc. I'm probably hitting them first with soft plastics. If I don't see any obvious cover, I'm hitting points, coves and rocky land areas that look like they might extend into the water.
When I don't see cover, I'm ALWAYS starting fast. Lipless and lipped cranks, spinnerbaits(if it's windy) buzzbaits, swimbaits etc. Why start slow if there might be a fast bite on? You'll never know if there's a fast bite if you start off with a slow bait. If there's a fast bite, don't ever waste it, as you'll put way more fish in the boat then if you were fishing slow on a "fast" day.
I'll work all levels of the water column until something works. If nothing works, for 15 or 20 minutes at each depth I slow it down a little. Perhaps fish deeper with a Carolina rigged lizard or other nice soft plastic. Fishing with a C-rig also allows you to feel the bottom and figure out where on a new lake there's humps, brush, saddles, dropoffs, holes, rocks and changs in bottom composition. It's a great bait to learn a new lake with if you don't have a depth and fish finder.
I'll fish the C-rig in different spots for 10-15 minutes at each spot, trying to disect the spot the best I can. If that doesn't work, I slow down even more as well as downsize my bait choice. Usually I'm catching fish by then though. If I catch nothing at all after 3,4,5 or 6 hours I'd be pretty discouraged. I'd go to the lake again and if I caught nothing again, I'd probably be hitting another lake from now on, but that's never happened.