The tricky bit is realising that the melody switches from one voice to another on their songs - according to Lester.

Start with the bass note.

If you pick out the melody on the guitar it often helps to find the chord that it fits in to.

I think I've got it for 'Polly' and '24-7' but I wouldnt want to swear to it.
There are subtlties that take a while to work out.

Good luck, be patient.