Step 4 of 5
Leave room for the tail
The last dot is the last cell, and the dots come in order. Keep both in mind.
The rule of thumb: The last dot must be the last cell, so keep a way into it open until the very end.
The path meets the dots in order and ends on the last one. That rules out edges you might otherwise be tempted by. Two stretches that would carry dot 1 straight into the finish while cells are still empty can never be joined: the path would end before it has filled the board.
The same thinking guards the order of the dots. If joining two stretches would put dot 4 before dot 3, or leave out a dot that has to sit between two others, that edge is out. Two dots that sit side by side but are not consecutive can not be linked either.
Early on, order is what turns a crowded board into a short list of choices. The practice boards show an early-finish ban in action, and none of them can be solved without the order rules.
Where to look: Dots that sit next to each other, and any stretch that touches dot 1 or the finish. Ask whether joining it would end the path too soon or break the count of the dots.
Worked example
A real position from a board that needs Leave room for the tail. Purple ring: what the reasoning rests on. Grey line: links already known. Dashed: the edges in question. Green line: a link it proves. Red cross: an edge it rules out.
The ends are guarded. Last step: using the finish as a starting point. Step 5: Work backwards →