Diz,
There are many ways. Of course you send your work to a publisher for evaluation. Even if it is good, expect several rejections.
I have published mine on
www.sibeliusmusic.com You can charge what you want and they have over 50,000 scores. Of course, you must be using Sibelius or Finale software, and they will only accept a couple from Finale.
On my website I have 3 areas for Sibelius Scores:
Trumpet Music;
http://www.ibowtie.com/storesibeliustrmpt.html
Brass Quartet Music:
http://www.ibowtie.com/storesibeliusbrassq.html
Trombone Music:
http://www.ibowtie.com/storesibelius.html
What I have done on my pages is sifted through the scores and picked out ones that are good (of course, my opinion) or interesting. I plan on doing it for concert band arrangements and brass band in the (hopefully) near future.
Many of these arrangement are cheap or free. Sibelius REQUIRES that each composer offer at least one arrangement for free.
If your piece is good, it gets voted on for the top ten. Several of the top ten pieces have been picked up by publishers. I know three of my friends have had theirs published. They have a discussion board also. If you are brave, you can ask the board to listen to your score. If they like it, they will vote for it. If they don't, you will get a critical analysis.
Some of my arrangements have done pretty well there. I don't charge for any of mine because I don't care about a few bucks -- I care more that my hymns get sung and my brass arrangements get played.
Obviously, I would recommended SibeliusMusic.com Sending something to a publisher takes a lot of time, a good recording, and being rejected even if it is good (you have to be thick skinned).
All the best!
M&C