1 - Mr. Steadie Eddie ... think like a train
A lot of acoustic players either just have one or two patterns they try to shoehorn into everything or if they do pick up on the groove their pattern changes randomly. Acoustic guitar is a rhythm instrument so the strumming pattern has to be rhythmically consistent with and utilize dynamics (loud and soft as needed) Practice with the recording or use a metronome or click track ... it really helps.
2 - Feed off the drummer ... find the beat of the song
Strumming patterns can imitate a drum groove. What's the accent beat 1 and 3, 2 and 4? Feel the groove and play the main beat louder the other beats softer. Muffle your right hand against the strings to add variation. Use bass notes as much as you can.
3 - Use power chords ... A, E & Drop D
Create open ringing sounds with cheat chords. Asus, Dsus, E chords up and down the neck and let the high b and e stay open. Utilize as many open strings as possible and learn some nice substitute chords that work well over basic chords.
4 - Complement the other guitarists - use a Capo
If you are playing with more than one guitarist, play in different registers. Or if one is strumming have the other guy picking or playing higher chord voicings. Two acoustic guitars playing almost the same thing gets to muddy. Also learn to use a capo and play in another complimentary key - just transpose the chords as needed.