A: My take on recording:
1. Half the battle is your sound. Going from Rock to Soul or anything else for that matter has a lot to do with your guitar and amp. Listen to some of the best players and ask yourself how he is getting that sound. Is it a telecaster or a Les Paul? Which pickup is being used? Is it a Marshall, Fender or VOX?
2. Simple is usually better unless they say otherwise. You always play more than you think (at least I do) so simplifying isn't a bad thing. A lot of Soul for example is just a convincing chord on 2 and 4 and nothing more. Conviction and a good tone count for just about everything sometimes.
3. Sessions are mostly done at home these days. If you had emailed me ten years ago, I would have told you to get your reading chops together. But these days I would tell you to get your recording chops together. At the college I run here in Tokyo I've made protools a required course for all students. Reading is obviously important but when you record parts at home you have very little time restrictions. You have to send the client a dry wav file but I'll often mix the guitar wet against the track to show them how I imagine the part should be mixed. So I send the dry wav plus a mixed mp3 of the song. Of course the client will mix it how he likes but sometimes it helps to give them an image. The problem with recording at home is the utter lack of conversation and creative input. You don't get any chance to talk to the other musicians about how to come up with something fun and interesting anymore or how the part could be mixed with the engineer or producer.
4. Good working instruments. Things that you sort of take for granted will screw up your sessions. You really have to make sure that your intonation is right on and there isn't any blatant fret buzz. I used my old Strat on a session recently and realized that the guitar isn't perfectly in tune all over the place. On the song I was doing, I had to play arpeggios up and down the neck on the top strings and I found that a D chord down at the bottom was in tune but when I played the D chord in the middle of the neck, it wasn't really in tune. My Strat is old and I don't think they were very particular about intonation in those days. The guitar is great for a Blues or something like that but won't really cut it for a modern sounding track. This sort of goes back to answer #1 but picking the instrument is important.
5. Be prepared to change your approach. Sometimes you think a Strat is right and the producer wants a Les Paul sound. It's as simple as that. Be prepared to switch instruments. Sometimes you think busy is good and the producer wants something simple.
6. Know a lot of music. If you want to come up with good parts, learn a bunch of music. Buy yourself the best of Wilson Picket and learn the songs and you'll be able to come up with good Soul parts. Buy yourself a Mike Landau CD and listen to all the sounds he gets. It's all about experience.