To support the post, I started getting commissions and public performances when I took the Juilliard's Evening Division's composition course with a teacher who ensured we wrote drafts and final versions for perforrmers every one to three weeks. One day an organist said he liked my draft and asked if I would finish it for an April concert. I submitted a final one, he made some recommended cuts and changes, I obliged for most of them (he is an excellent musician) and viola my first commission. It was unpaid but I got a good recording and have a good friend who is fine a musician. After your first commission working with a performer and hearing your work played well, you'll want to find other performance opportunities. The first few came from my class as I met undergrad and grad student performers at Juilliard. Strangely, not everyone in my class took full advantage. I will say I paid performers whenever I could. If I could not, I was honest and let them decide if they ever want to do it on their own with me as a consultant.
And don't burn bridges if you can ... I got the commission (unpaid) for an opera scene because my OLD comp teacher was on the board of this new performance organization. And befriend your professors and go to your colleagues concerts as well as reaching out once in awhile to new music. As maestro said you have to be a little affable.
Now, note that I have not been paid yet, but as maestro points out, a live recording is a great form of compensation for solo, chamber and vocal works. For your first orchestral or musical dramatic work, a live recording is fantastic but due to the labor there is a point you need to be paid for something. That goes eventually for the smaller works. I advise joining ASCAP, BMI, SECAM. With these agencies you can sign up for a small fee as a publisher to get some royalty in addition to small compensation for performances of your works.
Maestrowick forgot one area composers overlook for employment - church musician jobs. The scope can vary from something that requires only a few hours of practice in one week and pays about $8,000 a year for one service per week which you could play the piano to a full fledge Director of Music position requiring a good 25 hours to rehearse music and prepare a choir, another 15+ for paperwork, researching new music, organ/library maintenance. For these positions pay ranges widely depending on geography, in NYC you can make up to 80K a year but the normal range is 20K - 40K. Outside of NYC metro area the rates drop (well the exception are wealthy communities with a long history of involvement in music and arts, eg Scottsdale, AZ) . However, there is room to give lessons and do concerts during the down times when instead of 40 - 50 hour weeks you are doing 20 hour weeks. Great time to participate in composition retreats, perform or work on commissions. Even for singers this works as churches always need good choral leaders and vocal coaches - just build decent keyboard skills and basic, solid conducting skills. My point is you can find a wide array of positions to fit your professional goals and economic needs. You don't even have to go into this as a steady Sunday position, the skills gained are great for subbing at churcheswhen you want.
For all of the above though college and grad school are one of the BEST arenas to develop the contacts - not all musicians studying at the conservatory are going to be classical musicians, many crossover to pop, folk-pop-classical fusions, electronics, film and media.