I’m stating the obvious here, but since you’re paying your hard-earned money to a recording studio for their time, it’s in your best interest to go in prepared and maximize your use of their expertise/facility.

So, here’s a quick check list of what to do before you head to the studio.  Don’t skimp on this — it can really affect how your recording will come out.

• Figure out which songs to record.
• Know the keys to all the songs.  Experiment with tuning/capo before going to the studio to figure out the key that sounds the best and/or is the easiest for the singer (the most important consideration)
• Know the tempo to all the songs.  You don’t have to use clicks if your rhythm section is solid, but still, figure out the precise BPM (beats per minute) of every song before you go in.  Recording, like playing live, can affect your mood and make tempos feel fast or slow — you don’t want to rush or drag just because you aren’t in the right frame of mind.
• Record your songs.  Wait, you said before going to studio… yes.  Tape your rehearsal, and listen to it before heading to a recording studio. It will reveal issues with songwriting, arrangements and performance.  By all means, address those issues before going into studio.
• Put new strings on your guitars.  New heads on your drums.
• Write out settings for your effects/amps.  They may change during sessions, but you’ll know where to start.
• Make sure all your everyone knows when and where to show up.
• Type out lyric sheets.  You think you remember words to your songs, right?  But actually, in studio you’ll be thinking of a lot of other things besides the words — and it sure helps to read off lyric sheets, so you have one less thing to compute with your brain.  Make sure the font is big enough for you to see.
• Get good sleep.  Not just the night before, but 2-3 nights before.  Think you perform your best when you’re sleep deprived?
• Eat a solid meal.  The same as above.  Empty stomach = grumpier mood = think negatively.
• Show up before your schedule time.

Did I miss anything?  Please add them in the comments.