The next thing to think about is where on the billet the pattern is being formed.

Types of patterns. I break the different patterns into two families: Face grain patterns and End grain patterns. These refer to the position on the billet where the pattern is developed. (see attachment) 

There are some patterns that use the sides as part of the pattern, like an interrupted twist, but most of the typical patterns I can think of are developed on the faces or the ends.

Examples of face grain patterns are Raindrop, ladder, twists, and random. 
Examples of end grain patterns are W's, feather, and some mosaics.

There are patterns out there that use multiple bars to develop. The bars can be the same pattern (Turkish Twist is an example) or a combination of differently patterned bars joined to create complex patterns.

Understanding the basic mechanics of pattern development is the foundation of making PWS. Understanding that each of these patterns can be achieved through different methods, each method providing slight variations to the end product, is also foundational to creating PWS. 

For instance, ladder pattern can be created by pressing grooves and grinding down, or cutting grooves and forging down, or grinding grooves and forging down. Each method will produce a "ladder" with slightly different appearance than the others.

Understanding the different methods of manipulation also allows you to "think backwards" or reverse engineer to create a pattern. Looking at a pattern that someone else has created that you would like to reproduce, or drawing a pattern you would like to create, requires you to reverse engineer the steps from finished product to original billet or billets. 

Another more experienced maker could explain how they make a pattern to you, but without the foundational knowledge of how pattern manipulation is done, it would likely be gibberish. The best thing you can do to gain this knowledge is to experiment with pattern development, either in steel, or modeling clay.