Can I charge the seeker missile without wasting a missile in Metroid Prime 3?
Solution 1:
If you fire a regular beam charge shot and then immediately hold down the missile button, you should be able to start charging the seeker missile without having to "waste" a shot.
The key is to begin holding down the missile button during the "cooldown" period of the charge shot animation (when you are unable to fire anything, beam or missile).
Solution 2:
Go into Scan Visor. Press and hold d-pad down. While holding d-pad down, tap (A) to return to Combat Visor. You are now in Seeker missile lock-on mode without having fired a missile.