Since Coldplay broke onto the scene in 2000 many worship songs have Coldplay-esque guitar parts. I think it’s partly because it suits the style of many modern worship songs well and partly because it doesn’t require an advanced technique to play credibly.The basis of the sound is generally acknowledged as playing 8th notes i.e. 1 & 2 & 3 & etc as down strums and combining open and fretted strings together. The trick is then to also add delay on the crotchets or quarter notes. You’ll only need a couple of repeats but set the repeat level or mix quite high. This will have the effect of ‘thickening’ up your guitar sound and as long as you get the tempo right it should help to drive the rhythmic element of the song along.
Make sure that the open strings you play are in are key. Either the first note or 5th note of the key works well or an open string that is one of the notes in the chord you are playing over is good too. If the song is in a non open string key, don’t be afraid to experiment with a capo. It’s a tool to help you make sounds, not just a crutch to make non guitar friendly keys easier.
For the fretted notes try walking up and down a single string and find notes that work in harmony to the melody line, much like a backing vocal part. What you are looking for is a good spread of drones, octaves and 5th so try working between frets 7 and 12 for the fretted notes and see what you come up with.
Sounds-wise Johnny Buckland uses a semi hollow Thinline Telecaster with Fender humbuckers into a Fender Deville amp. This gives him a thicker tone than a normal Tele but still doesn’t loose the treble end like you may do on a Les Paul. Whatever setup you’re working with the key is to not overdo it with the distortion and turn up the ‘Mid’ control if you have one on your amp. What you are trying to achieve is that ‘clean but dirty’ sound that comes from having the volume and tone knobs on your bridge pickup wide open and hitting the guitar reasonably hard to push your sound into overdrive.
If you want to add some top end sparkle you can add reverb too but again don’t overdo it because it will have the effect of backing the guitar sound up in the house mix so your part could be much harder to pick out. Also try to resist the temptation of adding other effects like chorus is it may ‘sweeten’ your sound too much and you’ll loose some of the edginess of this rock based sound.
Lastly while this is a great tool to pull out of your guitar styles kit bag, make sure the sound fits the style of the song AND the style of what the other band members are playing, so use it well but use it tastefully, worshipfully and sparingly to make a statement at the appropriate moment.