Before linking nodes together, lay them out on the work area so that the logic flows from left to right and from top to bottom. Place your nodes so that the link coming from a source node are on the bottom or right side, and comes into the top or left side of the target node.
See the following example.
To link nodes together:
It doesn't matter what order you use for linking nodes, but it makes more sense to create the links in the order in which the logic flows.
If you try to link nodes together that cannot be linked, the status bar informs you that this task that cannot be completed.