Warm up before you get to the studio—Be sure you are thoroughly warmed up before you arrive at the studio. Develop a 20-30 minute warm-up routine that limbers and prepares up all aspects of your playing. This is not something that should be done at this studio. You should arrive ready to play at your best.
Bring a pencil—You've heard this since fifth grade band and it still applies in the studio: bring a pencil and USE IT. If you're going to be overdubbing other parts, go ahead and make any requested changes on the other charts too. In addition to a pencil, ALWAYS bring a music stand, assorted mutes, a stand light, valve oil and slide grease.
Know which microphones sound good on your horn and how to place them—Not every recording engineer and producer has experience recording horns. It would serve you well to research and know what kinds of microphones are commonly used on your instrument and how the microphone is commonly placed. For example, I love ribbon microphones on my trumpet. The Royer 121 ribbon microphone is a wonderful sounding mic on my horn, and I like the way it sounds when placed 2' to 3' in front of the horn. I carry a -10db pad with me to every session in case the studio is using a high gain condenser microphone and I am overloading the preamp. Carrying a -10db pad with me ensures that I have a remedy for this problem no matter where the session is and what gear they have.
Fine tune your headphone mix—Get your headphones mix right early on in the session. I like my mix with a fair amount of keyboard, a lot of drums, and a lot of high hat cymbal. The piano helps solidify my pitch reference (a much better source than guitar) and the drums help me clue in to the rhythm section's timing. I record with one ear off in order to blend well with the section in the room and not just through the headphones. I like a general blend of the horns in my headphones with just a little bit of reverb.
Four bars of pre roll—This is a personal preference of mine when in the studio. Most engineers I have found offer about two bars of pre-roll (lead in) before punching record on a take. As a lead trumpet player, I am most often responsible for leading the groove of the section with my playing. For that reason, I feel a little more comfortable hearing four bars of pre-roll so that I can internalize the rhythm section and really place the notes in the right spot.
Tune often—After you've warmed up be sure to tune! Tune to the track and to the others in the section. I have recorded in some studios that are cold as ice and others that are burning up. This kind of temperature deviation wreaks havoc on your pitch, so be sure to let your horn get adjusted to the room and tune and re-tune as necessary.
Breathe On The Beat—I learned this principle in college as I played in concert bands and orchestras. The conductor would ask everyone, even the percussionists to breathe together on the first note of the song. This ensured that we all played together and did not rush the entrance. I have applied this principle to all of my entrances in the studio and it helps me to find the song's internal pulse and not to rush the downbeats. Try it!
Don't Overplay—Remember this: Excitement in the studio doesn't come from how loud you play, it comes from how passionately you play. In other words, passion comes from the heart, not by how loud you can blow. Yes, sometimes louder volumes are necessary, but the louder you play the more difficult it can be to control your instrument. Internalize the emotion of the song and play every note with conviction, no matter what the volume.
Keep your air steady and strong—This is less of a studio-only tip and more of a general tip for all brass playing. When musical laziness sets in, air speed is the first area of playing that suffers. You must keep your airstream moving at a constant (and fast) speed into the horn in order to have a smooth solid sound. Your air speed should increase with ascending lines AND descending lines. Keep this in mind and you'll have a a big solid sound on the microphone.
Utilize visual cues within the horn section —When you're leading a horn section, use visual cues with your horn to indicate entrances and cutoffs for the other players in the section. This will help you play well together as a section. Session horn players are known to indicate the cutoff beat on the chart by writing a number that corresponds to the cutoff beat (1 = beat 1, 2+ = the "and" of 2, etc.).
Record overdubs with different instruments and mouthpieces—Producers will often ask brass players to layer (or stack) the same part multiple times to get a thicker sound. You may also be asked to record more than one part on the track. In this situation it can be extremely beneficial to record these parts on both different instruments and mouthpieces. By doing so, you reduce the amount of phasing that happens when the different takes are blended. This can make a huge difference in the sound of your tracks.
Communicate with the producer— I heard a story recently of a well-known LA session drummer basically refusing to do another take because he said, "Well, I could do another one, but I don't see why. I did it right on the last take." I guarantee you, this producer will never hire that drummer again. It is very important to offer an attitude of service in the studio. I call it a "willingness to accommodate." A producer needs to feel free to ask for another take from you for any reason. Don't forget, this will benefit YOU as well. With another take, you have a greater chance of sounding your best when the album releases.
Be Yourself—All of these tips are important, but above all else realize that you should be the best possible version of YOU. Don't attempt to be anyone else but yourself. We all have influences and that's great, but you have to find your own sound on the horn. That's why artists and producers will hire you again and again.
To sum it all up: thoroughly prepare, play with personality, and go the extra mile. Be a great hang and be thankful and courteous to everyone in the session. Follow these tips and play your best and you'll continue seeing more and more studio work come your way!