To create a high contrast black and white, you need to make really bright white and really dark black. Particularly during the post production stage, you will have to engage in more serious edits. When creating high contrast black and white images using Adobe Lightroom, you will have to determine the following key areas;
The tonal curve
You can bring up extreme black using the Blacks and the brightest whites using Whites. Apart from the blacks and white, you will have to work with the rest of the area of the photo. These areas are called midtones. You can work on midtones using the clarity tab if you need it to be done quicker. However, if you need a professional finish, with finest details, you have to use the tonal curves option.
You are free to play with the above mentioned tools and see how they help creating high contrast black and white images.