Step 1. The theme. I'm a big believer in finding my theme and then working from there to pick music, flags, props, etc. Pick a theme that suits your band. If they play jazz well then maybe do a prohibition show set in a speakeasy. Dress your guard as dancers and some as cops to do a raid.
Step 2. Shrink the field. Small bands on a full sized football field get lost visually and acoustically. You want to contain the action to the power section. Keep them inside the 35s, or even the 40s, and between the sideline and front hash. If you strategically place props on those yard lines and on the front hash it tends to close off the action and gives you a smaller stage. Instantly your band will look bigger. I've gone so far as to build back drops that ran 40-40 on the front hash. It also helps to hide guard equipment. As an aside, if you only have twenty wind players, I've had less, then at no point should their bells point anywhere but at the audience. We don't have the numbers to face towards the end zone and still maintain a triple forte.
Step 3. Use a floor cover. I like to make a floor cover out of used billboard signs. Our local ad company gives old ones away if you ask. Go ask. Take two or three and glue them together. Paint them to match your theme. One year my band did a murder mystery. To go along with that we made a giant Clue board. This helps to set the stage, while shrinking it, and gives you several new tools. One, new marchers have easy reference points to learn their drill. Second, it makes practicing inside simple. Provided you have the space. A bit of advice though, if you don't fix them in place they will move around on you. I put brass grommets in the edges and use tent stakes to hold it in place on a sod field. Practice this until your band can do it in less than a minute. On turf double sided tape will work the length of a show.
Step 4. Don't be afraid of electronics. If you have guitars, keyboards, basses, or whatever get a portable PA system to run them all through. If you have the budget. I've used a Yamaha Stage Pass to good effect. It will make mixing and balance easier on everyone. If possible I'd go ahead and find some one not in the band who can serve as a sound engineer on the field. Sound bytes are also perfectly acceptable to enhance the show. For the murder mystery we used clips from various comical shows like Pink Panther and Get Smart.
Step 5. Use what you've got. At one school I was at I had exactly one drummer. Obviously a percussion feature was out of the question. Instead we bought a trap set, built a rolling cart to put it on, and parked him on the side line. Essentially we had a rhythm section supporting the marching band complete with electronics.
Step 6. Don't think of it as marching band. I tend to think of my groups as choreographed rock or jazz bands before being marching bands. The difference is subtle I know. That doesn't mean the drill isn't important. I just keep it simple and fun. I have a friend who usually writes my drill and he knows what I like to use. A good simple box drill. A scatter drill. And a follow the leader. All look sharp but are pretty simple to teach and clean. One year we marched Chicago. Our mat was painted like a city lay out. The final move was a follow the leader down the streets. It looked great! It was stupid simple. Especially since the path was painted right in front of them. The cardinal sin is to overmarch them. However, don't let things sit still too long. There should be some motion somewhere to catch the eye.
Step 7. Think like a thespian. You have a highly choreographed jazz/rock/classical band performing a single act play. If possible, and if it will advance the story you're telling, go ahead and use actors to play parts. Going back to the murder mystery we found two actors to play the murderer and a detective. They were the highlight of the show. They also drew the audiences eye during halts. Again, some motion, somewhere. Going back to the last step, when you think of it as a play you think of your students hitting their mark on a stage.
1. Mark times are stupid. If you aren't marching then stand still. Don't mark time 24. I know that you can fix a multitude of sins during a mark time, but if you can't fix it in 8 then you won't fix it with 24. Just stand there tall and proud. It is also out of date unless you have a traditional military style band. But if thats the case this post probably doesn't have much to offer you. Now, there is a few occasions that I like to see a mark time. If everyone in a line is moving but one person, maybe they're an anchor point, I think they should mark time to match everyone else. Sometimes you just want to use it for effect. Maybe you want to use a retro style high mark time. Be warned though, there is a fine art to the high mark time. It is hard to perform well with out jostling the player around quite a bit.
2. Point your bells at the audience. Always. Unless you are at a carry or trying to get a specific effect. I've seen directors have their kids point their bells whichever direction they were marching with no regard to sound. I feel that really hampers the sound projection.
3. Despite what people say you can see a straight line from the front. Your kids are standing on a very large grid. If you want to use a company front, I do, then either work it till it's spotless or add a breakdown there to make it harder to gauge their perfection.
4. If a set isn't working either rewrite it or gussy it up to distract the eye. Don't give the judge a chance to find a mistake. Make him work for it.
5. Always focus on your bands strengths. Don't try to make kids something they're not. If they play rock well then let them rock. If they're a bunch of clowns then make the funniest show you can put together. Channel the Velvet Knights.
Anyway, that's my thought process. I'm busy trying to apply those steps to my show for next year. Take it all for what it's worth but I hope something in this can help you plan for next year.