Rehease you parts with just the drummer or without vocals, it may be likely you are asked to track to just the kit unless you are doing a live (band) recording, you would be stunned how easy it is to get lost without cues from the whole band in an arrangment without lyrics or a familiar melody. Maybe draw up arrangments on paper or chord charts.
You should remember to all tune up from the most expensive tuner that either your band or the studio own and after every couple of takes check the tuning.
New strings,
Best quality leads you can afford or borrow,
Batteries for pedals and basses,
Dont accept the phrase fix it in the mix. There are limitations to digital technology and although its possible to diguise faults in the playing (not that there will be im sure), you know they are there and the more you listen to the track the more obvious they become to you.
If your bass sounds good in the live room then it should sound the same in the control room if not better, again refernce to fix in the mix phrase.
remember you are the client, you should get the service you want from the studio not the other way round but dont ask the impossible.
But most importantly enjoy it and have fun, it is supposed to be a pleasurable experience creating music.
Good Luck