Standards Document 3 refers:
Corrections to heading or ETA shall be calculated rather than based on track crawling, impulse or inspiration. The applicant is expected to navigate by visual positioning in a practical way, not to feature crawl. Numerous heading or altitude changes that are the result of poor flying may constitute a fail in this section.
That's generally interpreted as, you must draw a straight line from a suitable set heading to your destination point. Fix points must be on that line, and many schools use an equal time method, by which every fix is 6-10 minutes after each other, ie 6 mins, 6 mins, 6 mins total leg time 18mins on the same track.
Radio navigation aids/GPS may not be used during the planned leg.
They may however be used during the diversion, but GPS only to provide Lat and Long data.
Hope this helps.