How do I make a zero turn map?

Zero-Turn Mapping, by Stephen Whitis.
 
Zero-turn mapping (ZT mapping, or 0T mapping) is a method of finding the locations of the dead ends, along with most of the warp paths, without using any turns. It doesn't give you any port information, so you still have to explore, but it can help with that exploring quite a bit. While it is possible in theory to do ZT mapping by hand, in practice it requires a utility. TWAssist and TWHelp both have ZT mapping options, as do the TWGuru scripts for the Amiga. Other utilities may or may not.
 
ZT mapping works by plotting lots of routes, and gathering the warp info discovered during each of those routes. The earliest versions used LD mapping (for Level Diagram.) A base sector would be chosen, usually stardock. From there, routes would be plotted to every other sector in the game, and from each of those sectors back to stardock. Better algorithms are available, which speed the process and manage to find more warps. The time needed to do ZT mapping varies quite a bit, as does the accuracy.
 
The algorithm used makes a large difference. The speed of the BBS computer, also, makes a large difference. Modem speed and the speed of the players computer can affect it, but not nearly as much as the others. Universe size, the number of one-way warps, and other factors also come into play. On a 5000 sector universe, a ZT map may take anywhere from 20 minutes to an hour and a half - possibly longer if a slow algorithm and a slow BBS computer are both being used. A good ZT mapping utility will allow you to map a bit at a time - if it takes an hour, you could do 10 minutes one day, 20 minutes the next, etc., until completed.
 
Having plotted these routes, they can be used in any good TW database. The database can then be used to locate dead ends. The best way to explore the universe is to fire etherprobes into dead ends, because its cheaper to fire a probe than to use turns to explore manually. That lets you save your turns for money-making. You don't have to use a ZT map to fire probes, but you can do your exploring with less probes if you know where the dead ends are located. ZT maps can also be used to locate StarDock and the Class 0 ports - which is useful in games where the SD location isn't listed in the V screen. SD and the class 0's will have six two-way warps, and an additional one-way warp into the sector.
 
Most games will have a small number of these, and checking them will locate stardock quite soon. It is also possible for a utility to use the ZT mapping information to calculate which avoids to set in order to force etherprobes to travel long routes before reaching their target. Dead ends are still the targets of choice, of course. This is useful, primarily, early in the game. In the early part of a game, most players are trading paired ports. By forcing the probes to travel farther, exploring more sectors, you are more likely to find pairs to trade. Later, when you've already got a number of pairs to trade, or have moved to other methods of money-making, using long-route eprobes isn't as useful.