Always bring as much and as wide a variety of tackle as you can. Having a few cranks, some surface lures, a broad range of plastics, and a number of spoons and spinners, in different shapes, sizes and colours, is best. Check gear well in advance to make sure everything is working. On lakes you know like the back of your hand, it might not matter much if your depth-finder conks out, but on a new lake, having a dead battery might be a disaster. The same is true for fishing gear.
Fishing is better than cursing.
Indeed, keeping a positive attitude is always important when fishing, but is critical when on a new lake. It helps if you can quickly boat a fish or two, but be prepared to spend time before the pieces start to fall together. Don't get exasperated. No matter how prepared you might be, fishing a new lake can be tough. Not every good-looking piece of structure will hold fish, but some will.