wave guns question

Do you have to plot to fire a wave gun or can you decide to fire it
during 
the fire phase thus allowing you to choose between the wave gun or other

weapons?

(yeah, an ON TOPIC post for a change)

btw, someone mentioned having moved to Miami.  We're playing Full Thrust
on 
Friday (21st) starting at 2pm at Dragon's Lair Games in Ft. Lauderdale 
(954-587-3347), and a few times next week.  Steve, my nemesis with the
uber 
MD2 WW2-era ships (ala Starblazer motif), is in town through next week. 
So 
come watch me get pasted with his die rolls (man, his average damage is
over 
1 per die.. is that usual?); or play on his side to handicap him (he
won't be 
making all the attack rolls against me).  :)