Les: Before you stain your Walnut, wait for a nice sunny day.
Grab your stock, a very wet washrag and go outside.
Use the rag to wet the wood and check out the darkness and color. If you like the look of the wet wood, then let it dry, whisker it and start the oil only treatment to finish it.
If it is too light for your liking, then go ahead and stain it.
I prefer Birchwood Casey Walnut stain but there are a lot of other good stains out there.
I usually delute it with some water or alcohol, apply a coat and then check it out in the sunlight when it's wet. If it needs to be darker, I apply another coat or two depending on the sunlite test results between each coat.
Whatever stain you choose, try to use water base, or alcohol base products.
If you use an oil base stain, you get what you get.
In other words, you usually can't darken oil base stains with more coats, and you can't sneek up on the color you want because the first coat usually oils up the wood so it won't want to take much more.