Pastry cook here, on the sweet side of things, my biggest piece of advice is to follow the recipe exactly if you don't know exactly what you're doing. Baking is basically science and if you don't calculate substitutions right, it's never going to come out right. Also make sure you have good ingredients. That box of baking soda from 5 years ago is not going to work that well anymore.

Not a professional chef, but if you've put enough salt in your dish and feel that putting anymore would over-season it, but you still feel it's lacking in taste, add some sort of acid.Lemon juice/zest, lime juice/zest, balsamic/red wine vinegar, apple cider vinegar - you'll be surprised at how much this lifts the dish!When I was getting interested in cooking, I would skip the acid completely because I honestly couldn't be bothered. I would always chuckle and joke at how much lemon/lime/vinegar chefs like Gordon Ramsay and Alton Brown put in their cooking.Then I tried it once.Now, every dish I make has some sort of acidity in it because it's just not the same without!