Sometimes, your tippet needs stepping down as well. This will ensure knots that won't slip. It can be confusing, so let's look at a simple wet design. We'll make a 100 inch wet leader for a four weight line, tapered to 3x. Of course, we'll use Maxima leader material, since it is stiff, and our favorite.
Variables are broad.
The fact is, you keep changing things until you get the system to present itself the way you want. The suggestions which follow on this page are a starting point. Generally, more butt will help straighten the leader, whereas more tippet will collapse the terminal end of the leader. Practice indeed makes perfect. Here's another, simpler formula for leader design.