1. Fresh strings! I like the bright roundwound tone and usually change strings every 4 songs or so.
2. When I can I do complete demos at home. The small recording devices like zoom h series are a great tool for that - just recording a song at a rehersal space can reveal a lot of stuff. Nobody hears everything going around them while playing and it`s quite common to miss some small discrapencies between instrumets. In my current band we record just the drums and add guitar and bass at home using simple line6 emulation.
3. Practice playing the exact songs you are going to recordd with a CLEAN technique. I once spent a week of playing them 10 hours a day right before the session. Painfully slow tempos, fingerings, dynamics - all of it.
It`s a good idea to check if you accidentally bend the notes out of tune durning passages that requie to move your hand a lot. Just stop at a random note, don`t move a thing and check with a tuner. It`s also important to be sure you mute all the unused strings - the method is pretty much the same. Happens to most of more often than you might think.
4. Bass is an instrument that needs a bit of finger noise, fret clack etc. to sound good. This might feel sloppy when isolated but makes the track much more alive even with drums alone. Some genres requie a lot, some very little but it`s usually there.
5. Have backup stuff like cables, strings etc. If you have a friend with gear MUCH better than yours - borrow it.
6. Few people can nail songs perfectly in a single take. I did it a few times but prefer to work on parts separately - I do the all the verses, then all the choruses etc. Makes things much faster and easier to change the tone/saturation level between the song parts.
7. Work as hard as you can BEFORE the session. But when it`s time to record try not to worry - just play and have fun. A good engineer will make you fell comfortable but nothing beats knowing that you did all you could to be prepared.
8. When I can I`m picky when it comes to the recording enginner - but when he is hired I let the man do his job. I trust his judgement and play whatever he asks me to play the way he suggests.
Number 6 is problematic to me. A player SHOULD be able to nail a song perfectly in a single take. I know I can, and most pro players can. If this is a demo for a cover band, I would imagine they want the recording to represent what they sound like. Recording things the way you describe won't accomplish that. Practicing alone until you can play the part all the way through with no mistakes is what will save the most time, and what pro session musicians are expected to do. I know way more bass players here that can nail a track in a single take than players who can't. If the first take doesn't cut it, I make sure it isn't my fault that it wasn't "the one".