I don't really have a field to go throw in, so I usually practice drives by throwing multiple drives on days, when the course is empty (i.e. I am not holding anyone up), but I can practice shots under 100 feet in my yard by using the trees as targets and obstacles. This has really helped my putting and short approach game. I usually only practice this way for about an hour or 2 a week, but you would be surprised by how much it helps get your form down, and helps you learn how far each disc will go. Since all but one or two holes at each course are under 350 feet, I usually make my second shot from within 100 feet. This extra practice time has already taken nearly 4 strokes off of my averages.
At work I can throw across the parking lot into small grass area with a couple of trees, which are right at 220 feet from my parking spot. On fridays, when everyone usually leaves early, I usually spend an hour working on my approaches before leaving early to get in a round or two. Once again, it has really helped me improve my form, and figure out which discs work best for me.
I have started to surpass my longer driving friends in scoring simply because they refuss to practice their putting and approaches. I have two friends you can drive 400 feet and land within 20 feet of the basket, but take 2 puts to get it in. With putting like that I can easily keep up with them on the long holes, and get enough birdies on the short holes to easily outscore them (one of them by usually 6 strokes)