If you are going to spend time on preproduction, be sure to make some test recordings to help locate the main core of the song. Take the test recordings out of the element of the studio to build up impressions of what is good and what is bad. Listening in your car can be a great way to honestly evaulate a song. It also gives you an idea of how the song will sound with all the background noise you get on the road. Depending on the genre of music, you might not care but if you are working on pop tunes, you want to be sure the song sounds good in a car.
For vocal songs, be sure to test your song in a few different keys to be sure that the singer can hit all the notes without bottoming or topping out. Even when the singer can hit all the notes, it's worth trying a few other keys to see if the energy level increases. Record a little bit of the song in a few different keys and listen back before making a final decision. A guitar with a capo is great for this. A half step difference can be huge.
Original instrumental music tends to originate at the correct key since that is often what sparks the creation of the song but it can still be helpful to test at other keys since that might put certain instrumentalists in a sweet spot on their respective instruments. Like vocalists, you want featured instruments to be able to hit all their best notes.
Refer to the Key page for more details.
Like picking the right key, picking the right tempo is extremely important. For vocalists, the tempo affects breathing and the amount of inflection you can put on a note. Typically, slowing down a tune gives singers more room to enhance a melody. The same goes for other instruments. If you are rushing, you'll be less likely to get in the pocket of a tune. There is usually a particular tempo where everything seems to come together.
A clue that you might be playing at the wrong tempo is if one or more players is having trouble staying in time. Try starting the tune at their tempo and see if it works for the other players.
Refer to the Tempo page for more details.
The musical arrangement of a song is obviously very important. Bands will often have historical arrangements of tunes that should be tested and refined. New songs typically need to be built up to the point where the core of the song becomes obvious.
If you are recording a band that has pre-existing versions of a tune you are going to record, listen to any existing recordings of the tune as a band and discuss how it could be improved. If the song seems dull, test the song in different keys and tempos. Try the song on totally different instruments; if it's a guitar song, try it on piano. If it's a piano song, try it on guitar, etc..
Depending on the recording situation, you may not want to introduce new songs at a recording session. If you are paying hourly, you don't want to spend that learning your parts. Spend some time in rehearsal getting the band familiar with a tune before commiting to paid studio time.
If your rehearsal space is set up to record, even better! Sometimes the best recordings emerge when you are "just doing a rough take". The pressure is off but still roll the tape (or Computer as it were) since these might be your best takes.
Developing musical arrangments for solo projects can be difficult but rewarding.
A click track is a machine generated timing que that provides a reference for the song. Though the tempo can be changed dynmically in most software recording programs, most recordings that use a click track have a fixed tempo that does not change throughout the song. Current pop music styles tend to have a fixed tempo but many of the greatest musical recordings ever made use a floating tempo that breaths with the song. There are advantages and disadvantages to both. Refer to the Click Track page for more details.