You can now download a pdf version of the entire vol.1 and 2 of the Progressive Method for French Horn on the "french horn method" page. This method also works well for trumpet beginners. There might be a few exercises going too low for trumpet but it mostly works. Of course, you can always buy the book itself on the "order books" page!

There be will pdf versions of vol. 1 for trombone, tuba and euphonium available soon. 

Check it out!

Before we start this topic, it is important to say that playing music is not an olympic sport. You won't get a medal for playing louder than your colleagues in a concert. In fact, playing louder than everyone else is a rather rude and selfish thing to do. Remember: it's not about how loud you can play, it's about how loud you should play. With that in mind, open your ears and use your artistic taste to determine your dynamics. Don't let your physical ability to blow in your horn dictate how loud you will play. 

Having said that, when the situation demands it, you need to be able to play a good forte or fortissimo. Developing a good dynamic range will take time and patience but if you work on it daily, you should see some fast progress. 

Here are a few things you can do to make more sound:

1) long tones with 8 beats crescendo and 8 beats diminuendo. Doing a few of these daily will help your tone and increase your dynamic range.

2)Breathing exercises. Take deep breaths and stretch your harms at the same time making a "T" shape with your body. This will expand your rib cage and increase the air intake. Immediately pick up your instrument after a few breaths and play something. You'll be amazed how good it feels.

3) Fool around a bit. A few years ago, I asked a colleague who could  play super loud how he did it. He said that he just spent a few weeks playing ridiculously loud just to fool around and that it worked for him... 

4)Embouchure building techniques. If your chops are stronger, you will be more relaxed in the high register and will get a better air flow to make more sound.

5)Don't be shy! Play with confidence. Go for it and don't worry about missing some notes. Your audience wants to be entertained. They don't mind you missing as long as you really try. Fear of missing notes will make you hold back and you won't be able to play as loud as you want. 

I'm sure there are a lot of other things you can do to turn up the volume but these 5 ideas should make a difference. 
Have fun!

The embouchure position varies from one instrument to another and there can be as many variations as there are players since no one as the same teeth and facial muscles. You don't need a "text book" embouchure position to perform well. As long as it's not completely off, it's better not to change anything if it feels good and sounds good. 

Some embouchure position might feel right at this moment but cause you problems in the future so it may be necessary to tweak it a bit. However, it is very difficult to predict what will happen so you might want to seek advices from more than one teacher before you do anything to your chops.  Be aware that it takes time and patience to adapt to a new embouchure position and the results are often mitigated. 

Here are a few simple guide lines on where to place the mouthpiece for all brass instruments:
 For the french horn, 2/3 of the mouthpiece should be above the line formed by your closed lips and 1/3 below as shown in the illustration on the left. 

Trumpet and trombone players will place it more or less  in the middle

Tuba players can play in the middle for better sound but can also play 2/3-1/3 as it makes it easier to reach some notes. 

Don't worry too much if your embouchure position isn't like what you see in books or on pictures online. I have seen people playing slightly on the side and still sound great. Everyone is different and it's more about how you feel than how it looks.

 Unfortunately, some teachers will have their students change their embouchure position into something that works perfectly for them but isn't necessarily what is best for the student. They end up doing more damage than good. I've seen many people with a fine tone losing their sound, strength and self confidence after studying a few months with a so-called great teacher who made them change their perfectly fine embouchure. Don't let this happen to you. 

If you do choose to make a change, consult two or three teachers.  Be patient as it will take time for your lips to unlearn what they are used to, adapt to the new feeling and build new muscles. Monitor your progress over weeks/ months and tweak the new position to make it your own. You will get better results this way.