EPIC.
Your looking for huge string sounds, throw down a bunch of reverb, build your orchestra hits from scratch, write at 50% volume so your hits are HUGE and your quiets are quiet. Download all the orchestral percussion you can, you can never have enough crash's, splashes, cymbal rolls, falres, timpani licks( which should be heavy and aggressive, but rare and un provoked), and especially gongs. Chimes make stuff sound pretty even when you can barely hear them, they're important. Build tension with harmonic minor scales, use fast attack strings at c 3 c4 and c5 to move your TRIPLE OCTAVE brass lines along. When your ready for somthing to sound bigger and better and all else fails, transpose it up a few halfsteps after your audience is familliar with the phrase.
Use the fast attack strings at absurdly high octaves with quarter notes in the root note of your progressions to generate some high pitched nervous tension and to make your slow powerfull stuff drive along a little bit.
The key to the biggest hugest loudest louds, is to make your quiets realllly really quiet. Dont build tension if your not going to release it, and never EVER start a track with the heaviest hardest part. Take the time to make an intro to damn near everything. If your bringing in the strings to back up a melody, introduce them, dont just add them on the next repeat. When all else fails, before you get to that transpose idea I talked about earlier, hold everything for a beat. Just stop and let your cymbals fade and then transpose it and go into it.
Tempo is important, but not as important. Just remember that the bigger, heavier stuff needs to be slower, dont get me wrong, things like Williams's "The motorcycle Chase" are epic, but its epic because its almost tuneless. You want power epic, you want simple concepts, but they need to be complex and technical.
Just remember, you can NEVER overwrite and have to much going on - unless you dont slowly build up and introduce it.
But nothing is worse than listening to empty boring music with giant gongs and acoustic driving percussion.
Listen to how retardedly simple Hans Zimmers scores are. He's good because he has interesting and endless ways of filling in his gaps between his absurdly catchy main themes. John Williams, he's good because fuck i'm ranting.