Hit and Run
A great strategy I have found is to use single shot missile
Basically build a ship with really poor system speed (for
the extra room) and fit the largest missiles with all the
trimmings (i.e. shields, armour etc) and set it so it fires
multiple missles but only one volley.
The idea being to build flotillas (4 core IF ships, no escort/picket
required) of these ships. Put 10 or so in a fleet and attack
In the actual combat screen, select all of your ships and
attack the planet. Then General Retreat to safety, since your
ships are now completely defenceless, and watch the desctruction.
Since the missiles are from lots of different flotillas, rather
than from one armada, they will seek other targets (system
defence ships, orbitals etc) if the planet's defences are
completely wiped out.
I have used this system particulary well against the Orions.
Sending fleet after fleet at the system will decimate any
defences, even if they are significantly superior.
The only complication is if the planet has no defences (i.e.
you destroyed them last turn) and you have to wait for some
other defences to show themselves. You may take casualties
in this instance. But on the plus side, these ships are usually
very cheap to build since you really don't need armour or