I see it all the time. An artist or band comes in and wants to record their new song, but they haven't figured out all the parts or who is going to sing what harmony, etc. Well, guys, the clock is ticking and I get paid by the hour. Do you really want to waste my time and your money figuring out the harmonies on the chorus in the studio? That's not a prudent decision. Do us both a favor and prepare, prepare, prepare!
So to prepare for your studio session, have the song's arrangement worked out and practiced well in advance. You should have refined your arrangement at home or at your practice venue and already know all the parts, what they require musically, and who will be performing them. Understand what instruments and gear you need to bring and what will be available at the studio, if you need those.
- Do plan to take time to familiarize yourself with the studio gear a little - for example most guitarists can't easily go from playing a Strat to a Les Paul for the recording sessions and still play with their same style - so be prepared for this.
- Do write things down - reading lead sheets, chords, or lyrics while recording is not a weakness - it's a strength and often bolsters your confidence so you can get your best performance captured forever.
- Do try to book time when you are at your best - if you always wake up with a froggy voice and you sing best at night, book your recording time at night. We're flexible! If you are sick, reschedule!
I'm not saying you can't experiment in the studio. Just be prepared to get your arranged sound down and then experiment with whatever budget you have left.