Notes for orbit changes using Maneuver Nodes:

• Prograde burns are the most fuel efficient at Pe.
• Retrograde burns are the most fuel efficient at Ap.
• Circle-izing burns are best done at Ap (and only enough to fix eccentricity).
• Normal / Anti-Normal (purple markers on Nav-Ball)  burns to match a target orbit's inclination are best done at the An/Dn intersection with the current orbit.
• Radial burns (cyan markers) are never very efficient.

Basically, if you want to speed up (make the orbit larger), you want to time your burn for when your absolute (or orbit) velocity is highest due to the Oberth effect.  If you want to change direction, time your burns for Ap (when you are moving the slowest).

Other tricks that are not immediately obvious:

• Left-click once on a maneuver node to select it and display the (6) buttons for adjusting the burn.
• Right-click once on a currently selected node to switch between the (6) buttons for adjustment and the (3) buttons that allow you to either delete the node or postpone it until a later orbit.
• When the (6) burn adjustment buttons are displaying, you can use the scroll wheel on the mouse to adjust the individual vector amounts (hover the mouse over the vector).  This is sometimes easier then grabbing the vector button and pulling it in/out using the mouse.
• When the (6) vector/burn adjustment buttons are displayed, you can use the center circle to move the time of the maneuver forward/backward along the currently projected orbit path.

Example of using the maneuver node to perform an adjustment:



Notes for video:

• Align your nav-ball on the blue target and leave it there through the burn.
• When the blue target runs away, it is time to stop the burn.
• Using the "m" key to switch to map mode and opening up the nav-ball at the bottom of the screen can give more accurate burns.
• Start your burn as close to the maneuver node as possible (usually 30s before is good).