Be well rehersed: knowing your guitar solos, back-up vocals and recording to a click will save you valuable studio time and money
The Click if you plan to record to a click (metranome) you must reherse to one. Figure out your song tempos before hand.
Equipment Maintance: A well tuned drum set with new heads as well as an intonated guitar with new strings can go a long way in making professional sounding recordings.
Factor in time for Editing and Mixdown more time spent editing/mixing = better sounding recordings