If your attacks are a little unfocused and you're getting a "trrr" sound instead of a nice "tah" when you're playing fast staccato and tonguing in different places in your mouth or on your teeth doesn't really help, you might want to try a more global approach to the problem.
My own personal theory is that the roughness in your attacks occurs because your sound is unfocused for a small fraction of a second in the beginning of each note. We very often forget about sound quality when we are playing fast notes. It is relatively easy improve your attacks if you improve your tone.
First play each note separately with your best sound. Do long tones with each note if you want. Then gradually play the "trouble passage" up to the desired speed. Always try to reproduce the sound you were making when you were playing the notes separately. Improving the tone quality for the whole note will automatically improve the tone quality for the beginning of the note thus improving the quality of the attack.
Although this might not entirely clean up your staccato, you should be quite happy with your attacks this way and it won't affect the fluidity of your playing.
"Happiness is not a station you arrive at but a manner of traveling"
-Margaret B. Runbeck
I saw that quote about 20 years ago on a poster. There was a guy walking next to a railway with these words written above him. Enjoy the learning process just as much as the results.
We all get frustrated sometimes when we can't play a passage or can't reach some notes. You might think that you are doing something wrong and need to change this and that. What if you just needed more time?...
If you're doing the right move, using the right fingering, blowing the right way, aren't too tired etc. you'll be able to play that passage eventually if you allow yourself a few days, weeks or months to learn it. You don't necessarily have to change your playing for every passage that doesn't work immediately!
If you expect perfection right away, you will only create stress for yourself which will slow down your progress.
We've all heard that playing music takes talent and practice but we often forget one element in the equation: time and patience. Progress will happen gradually if you're doing what you have to do on a daily basis. You'll be a bit better than yesterday and tomorrow will be a bit better than today. At the end, all these "a bit better" will add up and it'll be quite good!
The truth is that learning a musical instrument is a long process. It takes years to reach a certain level and once you've reached that level, you'll probably want to be even better! So when should you be happy with your playing?
The answer is: RIGHT NOW!
Not being perfect doesn't mean that you can"t have fun playing. Also being happy with your playing doesn't mean that you don't try to improve. We all know what we have to work on and are doing it but we also have to appreciate what we've achieved so far.
I am associate principal horn of the Singapore Symphony Orchestra and the author of the progressive methods. I'm happy to share my experience as a horn player and teacher with you.