1) Get with a good teacher. One who is now or has in the past played with a great symphony orchestra. They will help you with matters of style, interpretation, etc. There can be no guesswork.
2) Study the complete scores for all of these excerpts. You must know the style, context, and texture into which to fit your sound.
3) Listen to recordings....lots of recordings. Major orchestras under major conductors will be most reliable in terms of commonly accepted tempi, interpretations, etc.
4) Differentiate between how you play these excerpts in an audition and how you will perform them with the orchestra. An audition is played like a recital.
5) Research the music, composers, orchestras.....make
this a vital part of your life. Live with this music and allow
it to seed itself deeply in your conscious and sub-conscious mind.
The rewards are great. If you don't already, learn to LOVE this
stuff! Poke around on the Internet for as much info as you can.
You can start here at google.com