STOP a lot and look at what you are doing.......
Work in good light.
Learn to take what the stave will give you. As Jawge said, let the stave determine the design. Length width, specie, knots, etc... use them to manage expectations.
Pappy; "Never fall in Love with a piece of wood, it is just that, a piece of wood, it can break your heart and spirit, especially for a beginner." AMEN! It pays to know when to quit, when you are beaten.
Badger: "The front view should agree with the braced and drawn profiles." This is another short saying packed with info. I just spent HOURS trying to talk a beginner out of his misunderstanding that thickness helped "resist" set. Not all tillers are smooth arcs. If you want tiller help on here, please post a front view as well as a bent bow. Put the bend where it's supposed to go on that bow.
One of my favorites from Dean Torges: "Cast comes from dry wood, properly tillered."
Use ANYTHING that works for you. I am now married to the method that goes, "check, rasp, scrape, repeat", and the dogma of never pulling a bow harder than intended draw weight. I use black crayons relentlessly. I know a guy who thickness tapers his limbs by jamming on a complete set of metric wrenches down both sides of the bow. It works.
Don't overlook possibilities for dogma, but don't overlook dogma, either. I don't remember ever seeing or hearing of either a Native American bow of any style, nor European paleo or longbow made from plum, and yet the stuff in AMAZING. I can't seem to make a mistake with it.
Even dumb questions have answers.
Start with anything you can get your hands on, but buy the best tools you can afford as soon as you can after that.