Don't lie. You know you've done it before. "Honestly, I've been practicing hard!" Sure you have. Locking yourself in your room with a method book isn't really practicing unless you do something with that hour (hopefully) or so that you're in there.
How do you really practice, do you ask? You really practice by making it fun, and not trying to kill yourself. Play music you like to play, and never stop challenging yourself. I don't care if "Mary had a Little Lamb" is your favorite song in the whole wide world, it's time to move on! Let's start for the top.
I was once told that there was an orchestra player who could walk onto stage and blow out a double high G without warming up. The person who told me that said it was phenomenal. I think it's flat out stupid.
Warming up is essential not just to get your lips moving, but to give you a workout as well. It's a good idea to start warming up slowly, with lip buzzes and mouthpiece buzzing. Then, play a middle range note, like a G and hold it for a while. Start doing lip slurs to get your lips moving, and use harder slurs as you warm up. After that, play a few exercises, like double tonguing, intervals, or technique. The trick to really practicing, though, is to make it a little different each time. It's good to get into a routine, but overkill on routine flat out makes it boring, and when it is boring, your brain goes to sleep. How are you going to get better when your cranium is snoozin'? Also, don't kill yourself by playing constantly without a break- it just wears you out. About every five minutes, put the horn down and go get a little something to drink. Walk around the room. Whatever. Just give those chops of your's a rest.
Warm up should last as long as you feel comfortable. It is always a good idea to end your warm up with your scales. If you have time, play all fifteen, as many octaves as you can. This really builds endurance and range, so never knock the scales. If you don't have that much time, play the scale of the piece of music that you are about to practice.
Face it. You practice because you want to get better (unless you are being forced to, and in that case you probably haven't read this far). Practice your main exercise, etude or solo for the week or month. The big thing to watch out for here is that you shouldn't dwell too long on any one piece of music. Even if it is your All-State music, you need some variation. If all you do is practice that one piece, you'll be an expert at that one piece (Sure, you'll have a cool looking jacket patch too). You need variety, not only to keep it interesting, but to give yourself a broad background. Most professionals don't specialize in one or two pieces of music. They instead are pretty good on many, and with a little notice can clean up the piece to performance level. That's the way to be (plus it's not as boring). If you don't have anything you are supposed to practice, find something that looks like it could challenge you. Pick a solo or even one of the excellent studies in the Clark Studies or the Arban's book to work out of. There's enough in the "Fourteen Characteristic Studies" in the Arban's to give you something to work on well into the 21st century if you started now.
That's Not All, Is it?
You better believe it's not over yet. After playing your really hard challenging piece, play a few things that are fun, just for you. Go get a movie soundtrack score, or a song off the radio, or a really good song from church and play it. Knock yourself out. This is your time.
When it's all said and done, and you've played all you want to play, don't put up your horn. Warm Down. Remember, you are an athlete just like a runner is. When a runner finishes running a long distance, they warm down. Your lip is a muscle, and it too needs to be warmed down. Play a few long note exercises and a few pedal tones to loosen you up. Now you can put that horn in its case.