Here's a quick checklist for getting ready to go into the studio:
The biggest mistake musicians make when entering the recording studio is failing to bring songs that have been carefully written, arranged, improved, and performed over time.
As is written in this overview at Ultimate Guitar Dot Com, you often need to “Hone It Till You Hate It”. This process is also known as pre-production. The four most important points of pre-production are Song Selection, Keys, Tempos, Arrangements.
A producer worth their salt will insist on some sort of pre-production work.
Here’s a great overview on Pre-Production from DiscMakers Pressing.
The producer is responsible for the final product and the engineer is responsible for recording and mixing it. Sometimes that's the same person.
Who is going to be the producer of this effort? It's an important decision. Heavily involved in your project, a producer will possibly attend shows and rehearsals, work on arrangements, check your equipment, recommend outside musicians, decide what songs to record, schedule sessions, even coordinate budgets. They will see your project through completion, and help you get the best takes.
A producer should understand the overall artistic direction, be organized, have great communication skills, a good personality, and should bring a great deal of music theory and technical know-how to the table.
A producer doesn't have to be an engineer, and you may see sessions where a producer and engineer work together. A producer will be calling the shots and raising the quality of the album project, and the best producers will bring out the best sound from the band and engineer(s) and capture it for the world to hear.
☐ Co-Producer (optional)
A co-producer will engineer an album and make suggestions / subjective comments in order for you to make the best recording possible. They’ll be active in assessing takes and suggesting sounds, arrangements, etc. Often times, they will jump into the session cold on the first day. Generally they will be the sole engineer as well.
An engineer knows how to operate the recording equipment in the studio, get sounds and accommodate the requests of the artist or producer. Sometimes, a producer will perform this function. An engineer worth their salt should be able to make quick decisions, set up headphone mixes fast, know every microphone in the studio, and get the best possible sound in any situation.
Without both producer and engineer skill sets present, you will never get the best recording that you can.