The preparation for a recording session needs to be much the same as for any performance....The only difference is that in some recording sessions you get to have a second chance if you weren't pleased by something<G>....

Practice your scales, intervals, flexibilities, with a wide range of attacks, articulations and dynamics....

Read new music every chance you get...And not just trumpet music, since some orchestrators don't really know the limitations of your instrument, you need to be able to have as few limitations as possible....

Always have all the horns, mouthpieces, mutes, and valve oil that you'll need(and make sure the valves are clean and well-oiled before the session begins)....

Arrive early, with an arsenal of pencils(including erasers) and look over the music thoroughly, and MARK IN the fingerings on any tough passages(even Mel Broiles does this), draw eyeglasses to draw your attention to meter/tempo/key/dynamic changes....

Practice some yogic breathing to keep you relaxed between takes(and don't forget to take the horn off your chops occasionally<G>), and have some water with you both to keep you hydrated and to prevent your mouth drying out(as can often happen in climate controlled/air conditioned studios)...

Also, wear layers of clothing...You may get very warm, or the air conditioning may chill you, so be prepared with a sweater or jacket, and a shirt over a tee-shirt, so if you're too warm you can peel or vice versa....

Finally, try to forget all the stress on letter perfect-ness(though that remains the ideal), and focus on the MUSIC....It can help to visualize the audience listening even though they're not there.....

Hth,

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Take Care!
Jeannie